Where does “balain” come from?

balain (Middle Breton) comes from Gaulish balano-, from Latin balanus, from Ancient Greek βάλανος, from Proto-Hellenic gʷə́lanos, from Proto-Indo-European gʷelh₂- — acorn.

Ancestry of “balain”, step by step

Step	Language	Word	Meaning
1	Gaulish	balano-	broom, broom plant
2	Latin	balanus	an acorn; a fruit or other object similar in form...
3	Ancient Greek	βάλανος	acorn; the tree that bears acorns, the oak;...
4	Proto-Hellenic	gʷə́lanos	—
5	Proto-Indo-European	gʷelh₂-	acorn

Every word from Proto-Indo-European gʷelh₂- →Every word from Proto-Hellenic gʷə́lanos →Every word from Ancient Greek βάλανος →