[KoRn]

I’ve always wondered: What exactly IS a “diddly squat”? People say it all the time, and it makes no sense to me....

[labette]

did·dly-squat also did·dly·squat (ddl-skwt)
n. Slang
A small or worthless amount.

{common vernacular in many places}

[Slings and Arrows]

I’ve always wondered: What exactly IS a “diddly squat”? People say it all the time, and it makes no sense to me....

You've never squatted and made a diddly?

[NonLinear]

I’ve always wondered: What exactly IS a “diddly squat”? People say it all the time, and it makes no sense to me....

To diddle is to waste time (among other meanings, of course...). The squat part may come from "squat and leave it", which pretty much means worthless as you may gleen from the imagery of the phrase. So a diddly squat would be a wasted squat, which would be totally worthless.

Along the same lines: You can frequently hear about something being "out of whack", but how come you never hear about it being "in whack" or better yet, "fully in whack"?

[OwenKellogg]

Diddly squat: