Where does “doppelt” come from?

doppelt (German) comes from German doppeln, from Old French doble, from Latin dūplus, from Proto-Italic *duplos.

doppelt (German): double

Definitions

Step	Language	Word	Meaning
1	German	doppeln	to double
2	Old French	doble	double
3	Latin	dūplus	—
4	Proto-Italic	*duplos	—

doppelt — Etymology, Origin & Word History | Etymology Explorer