Where does “octante-et-un” come from?

octante-et-un (French) comes from French un, from Middle French un, from Old French un, from Latin ūnus, from Old Latin oinos, from Proto-Italic oinos, from Proto-Indo-European óynos — one; single.

octante-et-un (French): eighty-one

Definitions

eighty-one

Ancestry of “octante-et-un”, step by step

octante-et-un traces back through 3 separate lines of ancestry.

via French un

Step	Language	Word	Meaning
1	French	un	an, a; one
2	Middle French	un	a, an; one
3	Old French	un	a, an; one
4	Latin	ūnus	one, single
5	Old Latin	oinos	one
6	Proto-Italic	oinos	cardinal number 1 Previous: n/a Next: *duō;...
7	Proto-Indo-European	óynos	one; single

via French et

Step	Language	Word	Meaning
1	French	et	and
2	Middle French	et	and
3	Old French	et	and
4	Latin	et	and; plus; though, even if
5	Proto-Indo-European	éti	beyond; over
6	Proto-Indo-European	h₁é	and, then
7	Proto-Indo-European	ǵʰe	Postpositional intensifying particle: indeed, at any rate, in fact

via French octante

Step	Language	Word	Meaning
1	French	octante	eighty
2	Latin	octōgintā	eighty; 80
3	Proto-Indo-European	oḱtódḱomt	eighty
4	Proto-Indo-European	oḱto(w)-dḱomt	eight-ten

Every word from Proto-Indo-European óynos →Every word from Proto-Italic oinos →Every word from Old Latin oinos →