O.E. ealu "ale, beer," from P.Gmc. *aluth- (cf. O.S. alo, O.N. öl), perhaps from PIE root meaning "bitter" (cf. L. alumen "alum"), or from PIE *alu-t "ale," from base *alu-, a word with connotations of "sorcery, magic, possession, intoxication." The word was borrowed from Gmc. into Lith. (alus) and O.C.S. (olu). Ale and beer were synonymous until growing of hops began in England early 15c.
"[A]t present 'beer' is in the trade the generic name for all malt liquor