Where does “commentatrix” come from?

commentatrix (Latin) comes from Latin commentor, from Latin -tor, from Proto-Italic -tōr, from Proto-Indo-European -tōr, from Proto-Indo-European -tor-s.

Ancestry of “commentatrix”, step by step

Step	Language	Word	Meaning
1	Latin	commentor	I consider thoroughly, think over, deliberate,...
2	Latin	-tor	-er
3	Proto-Italic	-tōr	Forms agent nouns to verb stems
4	Proto-Indo-European	-tōr	Derives agent nouns from verbs, denoting someone...
5	Proto-Indo-European	-tor-s	—

Every word from Proto-Indo-European -tor-s →Every word from Latin -tor →Every word from Latin commentor →