Oh man I just stumbled across a series of posts on the etymology of the words ‘beer’ and ‘ale’ which are obligatory reading for anyone interested in such questions. I wrote a little post on the subject a while back, but these are masterful.
In the first post, the author Martyn Cornell gives the words for beer in other languages, pivo in the slavic langauges and Cervesa in the romance family. One of the things I learned is that the latin word for beer, cerevisia, did not come from Latin ceres meaning grain, but actually has a (Continental) Celtic origin.
In the second post, Cornell investigates what Old English beor might have meant and speculates that it meant not beer but strong drink more generally and cider in particular.
Finally in the last post, he takes up the etymology of the modern words ‘beer’ and ‘ale’, which both prove remarkably intractable, but the post is worth reading anyway for the twists and turns in the telling.