When I was in college I took a course on the history of the English language, and for each class meeting we had to look up a couple of words and write their etymologies on an index card. It was great fun, and now I'm trying to do a similar sort of thing on the internet here. I expect that it'll be more interesting than useful (if indeed I even manage to be interesting), and I most likely won't be revealing any new information; but hey, what else do I have to do with my time?!
bread : Bread comes from the Old English word of the same spelling (though different pronunciation), but in Old English the word had the more general meaning of 'morsel' or even 'piece of food.' It descends from one of two proto-Germanic words—either *brautham ('brew') or *braudsmon- ('fragments, bits')—and it eventually replaced the original OE word for bread, which was hlaf (Hlaf, of course, lives on in the modern loaf). I don't know what the staff of life is supposed to mean, but clearly bread is important stuff, enough that it came to stand in for food in general. And more than food, too: the expression bread-winner dates from 1818 and people were using bread to mean 'money' by the 1940s.