So I’m making characters not on dnd beyond  and my bro is playing a tabaxi ( sorry for abbreviations or spelling errors I’m stuck with my phone) and I was wondering what I should do with pick another language. Should I just use the languages form that one section of the phb and race descriptions or any languages I can find ( for example languages from the monster manual). Also if this post belongs in another thread sorry

Ask your DM.

I am the dm and I was looking for outside opinions 

Traditionally I would stick with the languages available to the listing in the races or what can be found in the PHB.  

Ok

Oh yes, then if you are DM, I would say, as someone who did create a custom language and found it to be a hassle in terms of the game rules, just stick to the in-game ones.

Though it is more of a hassle on D&D Beyond than if you are using paper or something.

Make it fun and force them to use one of those ridiculous languages that just happens to exist. Let them know the Giant Elk language then wait until like... they get to some kind of murder mystery thing and the only witness is a Giant Elk.

Quote from TransmorpherDDS >>

Make it fun and force them to use one of those ridiculous languages that just happens to exist. Let them know the Giant Elk language then wait until like... they get to some kind of murder mystery thing and the only witness is a Giant Elk.

 ^This.  So much this. 

Quote from TransmorpherDDS >>

Make it fun and force them to use one of those ridiculous languages that just happens to exist. Let them know the Giant Elk language then wait until like... they get to some kind of murder mystery thing and the only witness is a Giant Elk.

 It kinda reminds me of how Thor can speak Groot's language (called Groot) in Infinity War lol.

Right on.  Basically as the DM it's up to you what's ultimately plausible.  Some games encourage specific languages be known, or give characters who know certain language certain advantages.  But, like fluency in Giant Elk, you can also have fun with it.  Basically, as the DM this is one of those completely up to you sort of things.  Some games languages aren't used at all.  Other times, they're important.  And still others they can be used as a sort of wild card gag to be planned by the DM or improvised by the player.  

I generally don’t make my players pick second or third languages at the start, instead I allow them to keep slots open through the opening levels of the game and fill them as required. Usually by level 5 if any still have open slots I then push them to make a choice. I do make the choices make some kind of sense. 

But I have 2 Tabaxi in my party, twins, They know common, another language, and Tabaxi, a language formed by a collection of words, facial expressions and purrs or meows. Very hard to learn but it means the twins can communicate in secret without anyone else knowing what is being said. Tabaxi is one language I didn’t allow any other character to pick because it made no sense for any of them to know it (tabaxi have a travelled from a different continent) 

It sure would be nice if you could create languages for your campaign that populated the list of base languages, and rename or remove Common.

My campaign setting is based on the ancient Roman Empire.  Latin is the Common Tongue, Greek is the language of higher education that came from a nation that the "Romans" conquered, and there are two more for the two other major nations in my setting.  It's a real nuisance to put them on character sheets in the D&D Beyond Character Builder tool.  You have to customize each character individually, because you can't just created a custom language and share it between your characters.

Barbarians shouldn't start out with Common.  They have their own languages.  It's just kind of silly to imagine a Barbarian who is fluent in Latin, and it's pretty strange indeed to imagine them speaking in Greek, since by definition, Barbarians are people who can't speak Greek.

Xanathar's lets you learn new languages, so as far as I am concerned people should be able to learn new languages if they like, but I don't want top deal with exact times, how much it cost or anything of the stuff in the book as part of character generation.  I'd also like to limit the number of new languages to one per level.

Amusingly, I have a Tabaxi Rogue in my campaign, and its a character I created for my Significant Other, so I customized almost everything and put in a bunch of jokes.  She speaks the following languages; Bad Latin, Common, Greek, Latin, Meowing, Orc, and Thieves’ Cant.  By my own rules, she should only be able to speak two languages at level 1.  Each of my languages has a little note when you highlight it that tells you how you got the language.  Bad Latin, when highlighted, says "swearing".  Latin tells you that it's the Common Tongue of my setting, Greek notes that "if you don't speak that, you're a Barbarian", Meowing says it's the Tabaxi native language, and Thieves' Can't may be listed as a language, but it isn't.  It's a dialect, you speak the same language as before, you just have special meanings for the terms you use.  (By the way, the whole "Latin and Bad Latin thing comes from a quote in the movie The Fifth Element; "I only speak two languages, English, and Bad English.")

So she's have to know how to Meow, because most cats do that, and it's her native language,  She'd need to speak Latin and Bad Latin (which isn't language), Thieves' Cant (that's not a language), I can't remove Orc (I could only change to a different one on the list), or Common at all, and she can't have Greek until 2nd level by my rules, which is a pity, since I like the joke, so I'm leaving it.

Quote from Geann >>

It sure would be nice if you could create languages for your campaign that populated the list of base languages, and rename or remove Common.

My campaign setting is based on the ancient Roman Empire.  Latin is the Common Tongue, Greek is the language of higher education that came from a nation that the "Romans" conquered, and there are two more for the two other major nations in my setting.  It's a real nuisance to put them on character sheets in the D&D Beyond Character Builder tool.  You have to customize each character individually, because you can't just created a custom language and share it between your characters.

Barbarians shouldn't start out with Common.  They have their own languages.  It's just kind of silly to imagine a Barbarian who is fluent in Latin, and it's pretty strange indeed to imagine them speaking in Greek, since by definition, Barbarians are people who can't speak Greek.

Xanathar's lets you learn new languages, so as far as I am concerned people should be able to learn new languages if they like, but I don't want top deal with exact times, how much it cost or anything of the stuff in the book as part of character generation.  I'd also like to limit the number of new languages to one per level.

Amusingly, I have a Tabaxi Rogue in my campaign, and its a character I created for my Significant Other, so I customized almost everything and put in a bunch of jokes.  She speaks the following languages; Bad Latin, Common, Greek, Latin, Meowing, Orc, and Thieves’ Cant.  By my own rules, she should only be able to speak two languages at level 1.  Each of my languages has a little note when you highlight it that tells you how you got the language.  Bad Latin, when highlighted, says "swearing".  Latin tells you that it's the Common Tongue of my setting, Greek notes that "if you don't speak that, you're a Barbarian", Meowing says it's the Tabaxi native language, and Thieves' Can't may be listed as a language, but it isn't.  It's a dialect, you speak the same language as before, you just have special meanings for the terms you use.  (By the way, the whole "Latin and Bad Latin thing comes from a quote in the movie The Fifth Element; "I only speak two languages, English, and Bad English.")

So she's have to know how to Meow, because most cats do that, and it's her native language,  She'd need to speak Latin and Bad Latin (which isn't language), Thieves' Cant (that's not a language), I can't remove Orc (I could only change to a different one on the list), or Common at all, and she can't have Greek until 2nd level by my rules, which is a pity, since I like the joke, so I'm leaving it.

 Barbarians speaking common in my game makes some kind of sense, partly because not all barbarians come from tribes in the middle of nowhere. The barbarian Minotaur in my game comes from a crime family where he was raised to be part of the muscle. So his “Barbarian” training was completed on the streets of the town he was in, learning how to collect money, or deal with rivals. 

But even if it was in the wilderness, Barbarian tribes need to be able to trade and deal and communicate with those they meet, they are not all simply savages, so common makes sense as the language of choice for this. 

I'm fine with them picking up new languages, including Common, but I think that's a choice they should be able to make.  If, for whatever reason, they don't want to speak Common, why should they have to?  I have a set of rules that covers learning new languages, and it's a pity I can't implement it.  At first level, they would have know their native language, because that's exactly what it is, the language they spoke as a native.  They can pick as many more as their intelligence score dictates.  A 12 would give them one.  They get one more each level.  Seems fair enough to me.

Imagine if you will, a Barbarian from the plains of the Campyra speaks only in Campyri.  They travel into the territory of the Empire, and they refuse to learn Latin, the common tongue of the people there.  At first, the frustration this causes to the people he considers weak, who have been corrupted by the ease of their oh so civilized life makes him happy, but as time goes on, he realizes that the party of adventurers has the same problems understanding him as everyone else, and these are people he really needs to work with, so he learns Latin after all, and just to be spiteful, he learns Greek, because that's what the really smug ones use.

I'd rather not, but I can imagine it, and it sounds like a drag for all players and DMs involved.

If you want to challenge the table with a character who doesn't speak the lingua franca of the game world, you can, but the Common default for player characters is a matter of utility in the game.  A barbarian PC who speaks Common does not mean every member of the Barbarian's group of origin (tribe, clan, folk, people, what have you) speaks it.  PCs are supposed to be exceptional types.  

If you want to pet peeve it and make a party Babel, you can though now you're besetting the party with a communication mini game, so make sure it's something your players want to play.

"I'd rather not"  Sure, that's fine.  "it sounds like a drag for all players and DMs involved."  I'm the DM, I don't consider it a drag.  As for my players?  That's their choice.  All I said is that they should have one.  When players do not have any choice, that's called "railroading" even in such a tiny issue as this.  I have a great many pet peeves, and yes, railroading is among them.

One other note.  "If you want to challenge the table"  Isn't that what being a DM is all about?

There's challenging and there's frustrating.  Do let us know whether frustrating communication among players in character adds value to your game beyond your own entertainment.  Your Barbarian story is just that, a story.  For the game to be played, sometimes things that might make for a good story are dropped for utility because there's a difference between you telling a story about one character, and a DM and table of players collaborating on a story together.  Folks who think they "know better" about language in the game may have a point about realistic or plausible language distribution, but they're forgetting the game has utility components, like the language "Common" (which you can call whatever you want), for reasons that make the game more enjoyable.

If I could actually remove Common or change the name, we wouldn't be having this conversation.  I am stuck with clumsy work-a rounds, and while I am willing to take that kind of effort, I doubt many other DMs care enough about such a minor issue just to satisfy a character concept.  It is clear you do not, and that's fine.

Quote from Geann >>

If I could actually remove Common or change the name, we wouldn't be having this conversation.  I am stuck with clumsy work-a rounds, and while I am willing to take that kind of effort, I doubt many other DMs care enough about such a minor issue just to satisfy a character concept.  It is clear you do not, and that's fine.

Is it that you don't like the fact that everyone speaks common (hence the Barbarian anecdote) or that Common is called Common?

I don't like that everyone has to speak common, and I don't like than I can't change the name.  It's not an "or", it's both.