Where does “bitheirm” come from?

bitheirm (Irish) comes from Irish bith-, from Old Irish bith-, from Old Irish bíth, from Proto-Celtic bitus, from Proto-Indo-European gʷiH-tu- — life.

bitheirm (Irish): bioherm

Definitions

bioherm

Ancestry of “bitheirm”, step by step

Step	Language	Word	Meaning
1	Irish	bith-	ever-, constant; bio-
2	Old Irish	bith-	ever-, constant
3	Old Irish	bíth	inflection of at·tá: ## third-person singular...
4	Proto-Celtic	bitus	world
5	Proto-Indo-European	gʷiH-tu-	life

Every word from Proto-Indo-European gʷiH-tu- →Every word from Irish bith- →Every word from Proto-Celtic bitus →