history - What is the historical process by which words formerly considered vulgar become simply rude words?

I have noticed a pattern involving vulgarities where the previous generation's evil words become accepted as merely off-color or rude in the following generation. Is this merely each generation's small rebellion against their parents? Does society get bored with certain blacklisted words and move onto different choices?

It seems that some offensive or vulgar words maintain their status far longer than others while some don't last too long. Am I simply suffering from an odd form of selection bias?

Other interesting observations are the choices of insults that particular communities choose to use. Online video gaming has become quite fond of "rape" which is probably a completely inappropriate word to trivialize as meaning pwned. That community seems particularly attracted to violent or overtly offensive terms. Is there a historic precedence for this? Are such communities related to the aforementioned shift in what is considered vulgar?

Answer

You might be looking for the word dysphemism here. See Euphemism & Dysphemism: Language Used As Shield and Weapon by Allan & Burridge.

I have a 20-year-old copy of the book, which I thought was out of print. But I see it's available here.

The authors discuss how certain social classes and segments may use words in a deliberately provocative way, to flout societal norms and demonstrate the countercultural status ("street cred" in current parlance) of the user. If the culture prevails or the wider society finds the words useful, they get adopted, or at least tolerated.

The term jerk-off, for example, was once considered well beyond the pale, but now is a casually derogatory synonym for fool. Similarly, the term motherfucker was once a deadly insult: if you called someone that you could expect to be involved in a fistfight pretty soon thereafter. Nowadays it's not uncommon to hear someone refer to himself as "a bad motherfucker" (cf. Pulp Fiction) and although it's certainly not a word someone would use in polite company, it has been defanged significantly.

And considering your example of the word rape, this has an interesting etymology.

rape ORIGIN late Middle English (originally denoting violent seizure of property, later carrying off a woman by force): from Anglo-Norman French rap (noun), raper (verb), from Latin rapere ‘seize.’ [NOAD]

So you can see that it referred originally to seizure and acquired the sexual connotation later. Now it may be on its way back to meaning aggressive seizure or conquest, though I doubt it will lose the sexual aspect unless a really handy term for that specific meaning variant comes along.