This is a catch phrase that originated in a TV ad in the late Eighties that featured super athlete extraordinaire Bo Jackson and rock'n'roll pioneer Bo Diddley (he's notorious for his famous box-shaped electric guitar). Basically, the term means that somebody doesn't know doodly squat.
The narrator says:
Bo knows football.
Bo knows baseball.
Bo knows weightlifting.
***********************
In the meantime, Bo Diddley cranks out the notes on his guitar.
Then he says:
Bo, you don't know diddley!
Bo knows football.
Bo knows baseball.
Bo knows weightlifting.
***********************
In the meantime, Bo Diddley cranks out the notes on his guitar.
Then he says:
Bo, you don't know diddley!
by I Saw U2 Live Twice September 19, 2007