Where does “toya” come from?

toya (Pali) comes from Sanskrit तोय, from Proto-Sino-Tibetan *s-turʔ.

Ancestry of “toya”, step by step

Step	Language	Word	Meaning
1	Sanskrit	तोय	water
2	Proto-Sino-Tibetan	*s-turʔ	—

toya — Etymology, Origin & Word History | Etymology Explorer