Where does “alo” come from?

alo (Old Dutch) comes from Proto-Germanic alu, from Proto-Indo-European h₂elut- — beer.

Ancestry of “alo”, step by step

Step	Language	Word	Meaning
1	Proto-Germanic	alu	beer, ale
2	Proto-Indo-European	h₂elut-	beer

alo — Etymology, Origin & Word History | Etymology Explorer