Is situ another word for grandma and in what country if it is?

"Situ" is not a word for grandma in any language. It's likely you're thinking of a different word, or perhaps misheard something.

Could you provide more context or details? For example:

* Where did you hear this word?

* What language were they speaking?

* Was it written or spoken?

With more information, I can help you figure out what word you're thinking of.