* A misspelling: It could be a misspelling of another word, such as "Ursa," which is Latin for "bear," or "Urtica," which is Latin for "nettle."
* A regional term: It might be a dialectal word from a specific region or language group.
* A coined term: Someone might have invented the word for a specific purpose, like a brand name or a fictional place.
To help determine the origin, it would be helpful to know:
* The context in which you encountered the word: Was it in a book, a conversation, a website?
* Any other clues about its meaning: What did the word seem to refer to?
With more information, it might be possible to track down the origin of "Urista."