Where does “quadragénaire” come from?

quadragénaire (French) comes from Latin quadragenarius, from Latin quadrāgēnus, from Latin -ārius, from Proto-Italic *-āzios.

Ancestry of “quadragénaire”, step by step

Step	Language	Word	Meaning
1	Latin	quadragenarius	number forty; forty-year-old
2	Latin	quadrāgēnus	—
3	Latin	-ārius	—
4	Proto-Italic	*-āzios	—