Where does “meiō” come from?

meiō (Latin) comes from Proto-Italic meiɣjō, from Proto-Indo-European h₃meyǵʰ- — to urinate.

Ancestry of “meiō”, step by step

Step	Language	Word	Meaning
1	Proto-Italic	meiɣjō	—
2	Proto-Indo-European	h₃meyǵʰ-	to urinate

meiō — Etymology, Origin & Word History | Etymology Explorer