Another interesting etymology (this is the kind of thing that catches my attention when I’m copyediting a dictionary): crew originally meant ‘reinforcement(s)’ in the military sense, as can be seen from the first citation in the OED, “1455 Rolls of Parl. 34 Hen. VI, c. 46 The wages of ccc men ordeigned to be with him for a Crue over the ordinary charge abovesaid.” It quickly started being used for any “body of soldiers organized for a particular purpose” (which would doubtless have upset sixteenth-century prescriptivists, had there been any) and then for any gathering or grouping of persons, especially one “engaged upon a particular piece of work.” It’s from Old French creue ‘augmentation, increase,’ the feminine past participle of croistre ‘grow,’ from Latin crescere. (Note that it’s not from the Latin past participle, cretum, which left no descendants in French, but was reformed on the basis of other verbs with past participles in –u.) This means that it’s historically the same word (except for gender) as cru ‘vineyard’—a word which, however familiar to wine buffs, hasn’t made it into Merriam-Webster’s Collegiate.