“diddly-squat”

This is a slang expression meaning “nothing”. When you say that someone knows diddly-squat about chemistry, what you mean is that the individual doesn’t know anything about the subject.

*After all the work I did, I got paid diddly-squat. *The property that we bought ten years ago is now worth diddly-squat.

Sourced from ‘Know Your English’ Series – The Hindu Daily, June 20, 2005.