Where does “raver” come from?

raver (Old French) comes from Old French resver, from Frankish hnapp, from Proto-Germanic hnappaz — bowl; cup.

Ancestry of “raver”, step by step

Step	Language	Word	Meaning
1	Old French	resver	to hallucinate; to be delirious; to wander about
2	Frankish	hnapp	cup, bowl, basin; cup, bowl; bowl, cup
3	Proto-Germanic	hnappaz	bowl; cup

raver — Etymology, Origin & Word History | Etymology Explorer