Where does “lehen” come from?

lehen (Middle Low German) comes from Proto-Germanic laihną, from Proto-Indo-European leykʷ- — to leave.

Ancestry of “lehen”, step by step

Step	Language	Word	Meaning
1	Proto-Germanic	laihną	that which is lent, loan; fief
2	Proto-Indo-European	leykʷ-	to leave

lehen — Etymology, Origin & Word History | Etymology Explorer