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!
by I Saw U2 Live Twice September 19, 2007
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Something really easy to finish or complete
This project is diddley dog simple, so you should be able to get it done ASAP.
by colbyco July 12, 2009
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A random assortment of items; often food or edible items, of which the person doesn't necessarily know the name of.
"I just got back from the candy store."

"Oh good! What diddley-dads do you have in that bag?!"
by Maccas75 May 30, 2020
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To do nothing. The word fuck at the end makes it worse than just doing jack diddley.
All my coworkers do all day is jack diddley fuck and I always have to clean up after the lazy bastards.
by jimmybomm April 21, 2022
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This is a person who preforms the act of shitting on a persons face. After they shit on the persons face of they eat the shit, and wait. When they have to shit they shit back onto the person who shat on them first and this begins a never ending cycle to get the scary wongle diddley donlge to not haunt you in the after world. If you do it enough times he will in fact not haunt you in the after life. But there is no defined number, you must find this out yourself
Man I would love to wongle diddley dongle that girl. I need someone so that lord wongle diddley dongle will not haunt me in the after life.
by Lord Dongle Diddley Dongle -JW September 25, 2019
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