Is there a name for the following phenomenon?

But Siobhan said we have to use those words [Special Needs] because people used to call children like the children at school spaz and crip and mong which were nasty words. But that is stupid too because sometimes the children from the school down the road see us in the street when we’re getting off the bus and they shout ‘Special Needs! Special Needs!’

The passage is from The Curious Incident of the Dog in the Night-Time and it describes something I’ve noticed about group labels. First, one group, which is socially disadvantaged, is labeled something, call it X. Then X becomes a ‘nasty word’, as Christopher puts it, so people who don’t want to offend the Xes start to call the group that was called X something new, say Y. But if nothing has changed about the status of the group (or if it has improved but they are still disadvantaged), other people promptly begin using Y as a nasty word, and the cycle repeats.

This is a part of the phenomenon that became marked in the 1990s as “political correctness”, but it’s been going on for longer than that (there’s a fairly long cycle of names for the group currently labeled black people, for example, going back much longer than that, as well as others) and the behavior labeled ‘political correctness’ is really a) the renaming part, whereas I want a name for the part where the word becomes contaminated and b) an extreme, and may be partly a political construct anyway.

I don’t know if there is a word for this phenomenon of words becoming contaminated in connotation because of their denotation. It’s fairly straightforward from a sociolinguistic point of view — because the word refers to a disadvantaged group about whom some people think badly, the people who think badly use it with a connotation of insult, and it gradually acquires a connotation of insult. Once it’s not desirable to give insult to those people, because of a change in their status or a change in culture (or both) a new word is required. It also applies to some extent to curse words — the words are taboo because the things they refer to are taboo, and any new words invented for the referents tend to also become taboo. (Although there is also a reverse process through which curse words are bleached, such as ‘suck’ and ‘damn’. Damn is less bleached, but I think on average it isn’t regarded as very offensive, and it’s certainly bleached of its original meaning referring to damning someone to Hell. ‘Suck’ is bleached for almost everyone younger than a certain age now, I think. I last got in trouble for it from a particularly obnoxious high school teacher; I generally don’t use it at work, but I doubt anyone would really notice or care if I did, whereas ‘damn’ or ‘shit’ are still things I actively try not to say at work even though they’re also fairly bleached for me.)

Anyhow, I’d like to be able to just use a word for the contamination/replacement process without having to describe it conceptually or by metaphor every time. How does everyone feel about “the epithet cycle”?