When a man is dressed as a woman, why do they say he is "in drag"?
-- Christie, Lemon Grove
The term popped up in the 1860s, 1870s, thereabouts, in England. It actually could refer to either men or women dressed crosswise. But usually men, because it was a theater term, and it was more common for men to play women's parts than vice versa. That much we know. The rest is a guess on the part of word historians: It was "drag" because the actors had to haul around the stage those long, heavy dresses, cloaks, etc., that women wore in the 19th Century. At that time, the only other meaning for "drag" related to the act of hauling things or to the things being hauled, so I guess we have to be satisfied with that answer.