Where does “*brėsɨx” come from?

*brėsɨx (Proto-Brythonic) comes from Latin brassica, from Proto-Celtic bresic.

Ancestry of “*brėsɨx”, step by step

Step	Language	Word	Meaning
1	Latin	brassica	especially cabbage, but including cauliflower and...
2	Proto-Celtic	bresic	—

*brėsɨx — Etymology, Origin & Word History | Etymology Explorer