This is definitely Truth in Television, as in European history, Latin, French, and Italian were this, and Persian has had this role in the Muslim world. However, I was more thinking of the use of this for a Con Lang in fantasy works. Often, whatever the common language is will be 'translated' as English, but this language will actually be shown. In light of the real life examples of this, one of these will often sound Latinate. Examples:
- In Mistborn, there is the Latin-like High Imperial
- In A Song of Ice and Fire, in addition to speaking the "Common Tongue" (i.e. English), Westerosi nobility are shown knowing High Valyrian, the Latin-like language of a likely Rome-like lost civilization. It often functions as a lingua franca in the series, as dialects of Valyrian are spoken on the continent of Essos, and so Westerosi who travel there will draw from their knowledge of Valyrian to communicate.
- Serioli is this in the Dragaera series, although not only is it not at all like Latin, it is a Starfish Language that is painful to listen to.
- In Discworld, the Quirmian language is basically French and aristocratic young women generally go to boarding school in Quirm. Also naturally in aristocratic use is the old Ankh-Morpork language of Latian.
- In The Elric Saga, it is frequently specified when someone is speaking The Common Tongue, or The High Speech of Melnibone.
Hello, Unknown Troper. You'll need to get known to lend a hand here.