Have I already written about nagging? Probably, but it bears repeating (get the joke?)
Nagging is a very gendered term, even if the web dictionaries mostly give it neutral definitions, such as
1. To annoy by constant scolding, complaining, or urging.
2. To torment persistently, as with anxiety or pain.
These are correct, as far as they go. But "nagging" is not a term we use when a man constantly scolds, complains or urges (Rush Limbaugh and Glenn Beck nag, by the way), unless we wish to point out that he is engaging in a stereotypically female behavior and should shut up.
Nope, it is women who are described as "nagging," and especially wives or girlfriends. The term is intimately linked to what goes on in heterosexual intimate relationships. Using the first definition given above, nagging therefore means a situation where the man is annoyed by the constant scolding, complaining and urging of his wife or girlfriend. Sometimes he is so annoyed that he blows her brains out.
Nagging is like "gossiping" or "bitching": Something negative which only women are assumed to do. But if you carefully define such verbs as to their real contents you will find that men engage in them, too. For example, gossiping about the sexual peccadilloes of politicians is politics because men participate in it!
Still, men might nag less than women, on average, and here is why: Though it is probably true that there are people who nag just for the joy of nagging or because they wish to torture someone, nagging is really the rusty weapon of the relatively-less-powerful.
To see why I inserted "relatively" into that definition, think of a workplace. Bosses don't nag to their subordinates, because they don't have to nag. Subordinates don't nag to their bosses, because if they do they get canned. (Instead, they "bitch" about the boss to each other which suggests that these pejorative verbs about female complaining are perhaps about the complaining of the less powerful in general.)
Nagging is not practical in a rigidly hierarchical setting. But heterosexual relationships may not be that hierarchical. Even the more hierarchical ones have openings for negotiation (who takes out the garbage, who does the dishes, who picks up the dry-cleaning) or at least for manipulation, something into which nagging can be slipped.
Put in different terms, "nagging" might be found somewhere along a straight line ranging from pathological behavior by the nagger to pathological behavior by the "naggee." Yet we tend to focus on the former end of the dimension when discussing the phenomenon.
To create an example closer to the latter end, think of a situation where one partner makes a completely reasonable request which the other partner refuses to hear or to respond to. Assume that this refusal makes life much harder for the one who made the original request. Assume, furthermore, that she/he cannot easily leave the relationship. What is the next step in these negotiations? It is not difficult to imagine that it might be renewing the request, in various ways. Which would be called nagging.
Sure, this might be a rotten strategy. But then what is the alternative?