The most odd language added on YouTube subtitles is probably Esperanto. It was created in 1887 by a Polish ophthalmologist, L.L. Zamenhof, as an international auxiliary language to break down language barriers between people of different cultures and backgrounds. Despite its interesting history, it’s not widely spoken today, making it quite the peculiar addition to YouTube subtitles!
But if you’re looking for something even more out-of-the-ordinary than Esperanto, check out Lojban—alogicallyl constructed language designed to be more suitable for machine processing than natural languages.
Additionally, there are several artificial languages (such as Volapük) that have been around since before the 20th century and could also make for strange yet fascinating YouTube subtitle choices. Whatever your weird language preference, you’re sure to find something interesting on YouTube!