Where does “millesme” come from?

millesme (Old French) comes from Latin millesimus, from Latin Mīlle, from Proto-Italic smīɣeslī, from Proto-Indo-European smih₂ǵʰéslih₂.

Ancestry of “millesme”, step by step

Step	Language	Word	Meaning
1	Latin	millesimus	thousandth
2	Latin	Mīlle	—
3	Proto-Italic	smīɣeslī	—
4	Proto-Indo-European	smih₂ǵʰéslih₂	—

millesme — Etymology, Origin & Word History | Etymology Explorer