The Devil's Dictionary: Hag
An elderly lady whom you do not happen to like; sometimes called, also, a hen, or cat. Old witches, sorceresses, etc., were called hags from the belief that their heads were surrounded by a kind of baleful lumination or nimbus - hag being the popular name of that peculiar electrical light sometimes observed in the hair. At one time hag was not a word of reproach: Drayton speaks of a "beautiful hag, all smiles," much as Shakespeare said, "sweet wench." It would not now be proper to call your sweetheart a hag - that compliment is reserved for the use of her grandchildren.