Here's an interesting observation from a piece in this week's New York Times Magazine about women's reactions to political wives who stand by their cheating husbands (or don't):
I’m speaking as a woman here, one of those who have watched the cuckold wives (a word that technically doesn’t apply to wives; I can find nothing in the dictionary that applies to sexually betrayed women, though you would think Webster would have added one by now) and mentally placed ourselves in their shoes.
In general, researchers tell us, men are more threatened by a woman having sex with another man, and women are more threatened by a man falling emotionally for another woman. Since most straying from marriage vows includes sex but does not always include love, men find it more threatening when women cheat than vice versa (which may well explain why they’ve invented a word for when it happens to men).
The American Heritage Dictionary defintion of cuckold: "n. A man married to an unfaithful wife" and "tr.v. To make a cuckold of." It also gives and etymology and interesting word history:
Etymology: Middle English cokewald, from Anglo-Norman cucuald, from cucu, the cuckoo, from Vulgar Latin cuccūlus, from Latin cucūlus.
Word history: The allusion to the cuckoo on which the word cuckold is based may not be appreciated by those unfamiliar with the nesting habits of certain varieties of this bird. The female of some Old World cuckoos lays its eggs in the nests of other birds, leaving them to be cared for by the resident nesters. This parasitic tendency has given the female bird a figurative reputation for unfaithfulness as well. Hence in Old French we find the word cucuault, composed of cocu, “cuckoo, cuckold,” and the pejorative suffix –ald and used to designate a husband whose wife has wandered afield like the female cuckoo. An earlier assumed form of the Old French word was borrowed into Middle English by way of Anglo-Norman. Middle English cokewold, the ancestor of Modern English cuckold, is first recorded in a work written around 1250.