Where does “fejből” come from?

fejből (Hungarian) comes from Hungarian fej, from Proto-Uralic päŋe — head.

fejből (Hungarian): by heart; elative singular of fej

Definitions

Step	Language	Word	Meaning
1	Hungarian	fej	head; head, mind, brain, intellect; heads,...
2	Proto-Uralic	päŋe	head

fejből — Etymology, Origin & Word History | Etymology Explorer