Where does “bleugaz” come from?

bleugaz (Proto-Germanic) comes from Proto-Indo-European bʰlew- — to swell, flow; to overflow, to gush.

Ancestry of “bleugaz”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	bʰlew-	to swell, flow; to overflow, to gush

bleugaz — Etymology, Origin & Word History | Etymology Explorer