Here's an example of a contemporary American slang word that I don't think came from African Americans -"pwned".

There are a number of entries from urbandictionary.com posters for the word "pwned". Here's one of them:

pwned   

"Unlike the other people who have posted definitions that are ridiculous, do not have substantial backing, or are simply mis-informed, I will give the complete definition of what "pwned" means.

1. The origins of "pwned" are debated but there are two possible sources:
a. A prominent quake player mis spelled "owned" and the new word "pwned" was adopted by people who thought it was "1337".
b. A warcraft map designer misspelled "owned" and thus people started using "pwned" instead.

The definitions are as follows:
In video games:
1. Completely annihilated or dominated.
2. Perfectly owned, meaning the other player did not do any damage.

I pwned your head with my awp.

OR

I just pwned your ass noob!"
-by jack Nov 17, 2003

http://www.urbandictionary.com/define.php?term=pwned&defid=835533

-snip-

According to Wikipedia, "pnwed" is "derived from the word "own"... that implies domination or humiliation of a rival, used primarily in the Internet gaming culture to taunt an opponent who has just been soundly defeated. Past tense is sometimes spelled pwnt (pronounced with a t sound), pwned, pwnd, pwn3d, or powned (with the standard d sound). Examples include "pwnage" or "you just got pwned".

In Internet security jargon, to "pwn" means "to compromise" or "to control", specifically another computer (server or PC), web site, gateway device, or application; it is synonymous with one of the definitions of hacking or cracking. An outside party who has "owned" or "pwned" a system has obtained unauthorized administrative control of the system."...

Use, online and in popular culture

The 2006 South Park episode, Make Love, Not Warcraft, satirized the game World of Warcraft. In the episode, the word is pronounced [poʊn] (pone), rhyming with "own".
"Looks like you're about to get pwned. Yeah!" - Eric Cartman (20m 30s into episode)
"That was such über-pwnage" - Kyle Broflovski (soon after above) ...

http://en.wikipedia.org/wiki/Pwn