What it means
Diddly-squat means absolutely nothing at all: zero, bugger all, not even a crumb with ambition. People use it when they've got no money, no result, no clue, or they've done sweet nothing. It's playful and a bit comic, but the point lands hard: the total is a big round nothing.
Usage examples
"After all that work the bonus was diddly-squat, barely covered a sandwich."
"I tried to fix the boiler myself but I know diddly-squat about plumbing."
"I have done diddly-squat all weekend, just sofa and a stack of crime novels."
"The new boss promised raises but in the end we got diddly-squat in the December payslips."
"They hyped the refund for weeks and I got diddly-squat back, cheers for that."
Where it comes from
It’s an American slang expression that shows up in the mid 20th century, built by stacking two older informal bits that both pointed toward nothing. The exact route is a bit messy in the records, but the sense is clear from the start: extra-emphatic zero, with a goofy sound that makes the nothingness hit harder.
