What is casu language?

There is no known language called "Casu". It's possible that you might have misheard or misspelled the name of a language.

To help me identify what language you might be looking for, please provide more context:

* Where did you encounter this term? (e.g., a book, a website, a conversation)

* What is the subject matter? (e.g., history, linguistics, geography)

* What is the approximate location or region associated with the term?

With more information, I can try to help you figure out what language you're interested in.