Where does “doupion” come from?

doupion (French) comes from Italian doppione, from Italian doppio, from Latin dūplus, from Proto-Italic *duplos.

Ancestry of “doupion”, step by step

Step	Language	Word	Meaning
1	Italian	doppione	duplicate
2	Italian	doppio	double, dual, two; two-faced, double-dealing;...
3	Latin	dūplus	—
4	Proto-Italic	*duplos	—

doupion — Etymology, Origin & Word History | Etymology Explorer