Where does “bōk” come from?

bōk (Old Saxon) comes from Proto-West Germanic bōk, from Proto-Germanic bōks, from Proto-Indo-European bʰeh₂ǵos — beech.

bōk (Old Saxon): book

Definitions

Step	Language	Word	Meaning
1	Proto-West Germanic	bōk	inscribed billet, letter; book
2	Proto-Germanic	bōks	letter, written message, inscriptions carved into...
3	Proto-Indo-European	bʰeh₂ǵos	beech

bōk — Etymology, Origin & Word History | Etymology Explorer