Pliny once wrote, "Indeed, what is there that does not appear marvellous when it comes to our knowledge for the first time?" On the opinion page of Saturday's New York Times (October 23, 2014), Kory Stamper ponders the apparent novelty of today's slang, only to caution readers to assume that all the cool argot is necessarily newly-minted. She observes, "Everyone knows that slang is informal speech, usually invented by reckless young people, who are ruining proper English. These obnoxious upstart words are vapid and worthless, say the guardians of good usage, and lexicographers like me should be preserving language that has a lineage, well-bred words with wholesome backgrounds, rather than recording the modish vulgarities of street argot."
Except that--like many things "everybody knows:--it's just not true. And so Stamper traces the "venerable roots" of some current slang as far back as the sixteenth century. You can read the entire column here: http://www.nytimes.com/2014/10/04/opinion/slang-for-the-ages.html
[Thanks to the authpr for permission to quote from her column and post this link.]