* A typo: Perhaps someone meant to type "try" or "too."
* A nickname or abbreviation: It could be a shortened version of a name or a unique slang term within a specific group.
* A foreign language term: It might have a meaning in another language.
* An internet meme or inside joke: Some online communities may have adopted a specific meaning for "tyy."
To understand the meaning of "tyy," you need more context.
If you saw it in a specific message or conversation, please provide the surrounding text or the situation where you encountered it.