Where does “erugineux” come from?

erugineux (Middle French) comes from Latin aeruginosus, from Latin aerūgō, from Latin aes, from Proto-Italic aos, from Proto-Italic ajos, from Proto-Indo-European h₂éyos — a metal, copper, bronze.

Ancestry of “erugineux”, step by step

Step	Language	Word	Meaning
1	Latin	aeruginosus	rusty, covered with copper rust
2	Latin	aerūgō	rust of copper, verdigris
3	Latin	aes	money, pay, fee, fare; copper, bronze, brass;...
4	Proto-Italic	aos	bronze, copper
5	Proto-Italic	ajos	—
6	Proto-Indo-European	h₂éyos	a metal, copper, bronze

Words derived from “erugineux”

eruginous
aeruginous

Every word from Proto-Indo-European h₂éyos →Every word from Proto-Italic ajos →Every word from Proto-Italic aos →