I always assumed you just rolled your face on the keyboard. Or threw rocks at it.
<fx: 1337 segway...>
So I was trying to come up with a reddit username. I'd reached my upper limit of "right, honestly there is no frickin' way somebody has come up with this one":
th3r315|\|0w4y50m3b0dy|-H45c0m3uP\/\/1t|-|1s0n3-123456pielevenbanana
"Username already taken" :-O
[In the interests of public decency I shall not repeat some of the usernames I tried]
...and then a friend suggests, "Hey, why not just roll your face on the keyboard?"
So, somewhat tangentially, my reddit username was born: 'FacerollOnKeyboard' :-)