Where does “Ғайса” come from?

Ғайса (Bashkir) comes from Arabic عِيسَى, from Hebrew יְהוֹשֻׁעַ — Joshua.

Ancestry of “Ғайса”, step by step

Step	Language	Word	Meaning
1	Arabic	عِيسَى	Jesus
2	Hebrew	יְהוֹשֻׁעַ	Joshua

Ғайса — Etymology, Origin & Word History | Etymology Explorer