I can't say this with 100% accuracy, but I believe the phenomenon could be traced back to early Hong Kong ganster films. Look to John Woo and Chow Yun Fat for more. Personally, I've held a Glock in that fashion and fired the thing--it's a more comfortable feel and I found it easier to aim (as much as you can aim with a Glock, at least...terrible accuracy). Mileage may vary.
I must admit that I was on a firing range and not the local 7-11 when I shot the gun.