Of course, as the word gets picked up by a wider base of users, the original users of it, the originators, may stop using it. Once slang terms achieve mainstream usage, they often lose their appeal, their covert prestige, among the original users. Look at it this way: if your mum is talking about bling (and she is - I heard her on the bus to Peckham yesterday) then you probably won't be. Slang gets rinsed out. Bruv. Or is it cuz. Or should I say fam. Anyway, moving swiftly on....
The slang term will probably then reach a peak of use - the top curve of the S in Bailey's model - before flattening out and dipping down. After a period of time - it might be 5 years, 10 years or longer - the only person left saying the word will be your mum and your English teacher.
So, is this what has happened to swag? In this article by Jason Richards, the rise and rise of swag is charted and the question asked (of linguist Geoffrey Nunberg) if it will stay popular (like cool) or die away. His response is interesting:
Almost all of these words come in and then disappear. Because that's the point—high school freshmen and young management consultants spin off new words so that their language sounds different from [that of] the old boys. Obviously, some of them do persist, but it's very hard to predict which ones will.
What's odd about swag is that while it now has very positive connotations - to get your swag on is clearly a good thing by most people's standards - it had a previous life not that long ago as a derogatory term. Back in the mid-2000s, swag meant rubbish, crap and useless. As Urban Dictionary entries from 2006 and 2007 reveal, it wasn't a term of approval at all, and I remember SFX students (always leaders in lexical innovation) using it in this way from around that time.
But it's clear that there's now been either a shift, or (more likely) a completely new meaning, bulldozing the older and more restricted usage of swag as crap into dust. Perhaps the usage of swag as crap was geographically restricted, or it never achieved the same level of acceptance among people with covert prestige to catch on more widely. Perhaps there was a word occupying that slot already that prevented swag from catching on as a derogatory term (perhaps waste, or moist took the title). Maybe, the support of the likes of MIA and Puff Daddy/Diddy/whatever he's called gave swag as stylish, good, cool the push it needed to take it into an upward trajectory. And the rest is history, but for how long?
Edited on 14.10.11 to add links to two Nancy Friedman pieces on swagger, swag and schwag