Where does “sermō” come from?

sermō (Proto-Indo-European) comes from Proto-Indo-European sēr-, from Proto-Indo-European ser- — to flow; to guard; to bind, to tie together.

Ancestry of “sermō”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	sēr-	—
2	Proto-Indo-European	ser-	to flow; to guard; to bind, to tie together

sermō — Etymology, Origin & Word History | Etymology Explorer