Last month they looked at the word "Diddly Squat" and here's what they had to say:
Part of Speech: Noun, mass (no plural)
Meaning: (US Slang) Next to nothing, something worthless, or even nothing at all.
Notes: This odd bit of US slang contain two words that are nearly synonyms of each other and the compound they appear in. "He didn't do diddly," "He didn't do squat," and "He didn't do diddly-squat," all mean pretty much the same, except that the compound is a bit more emphatic.
Word History: Today's Good Word is a US variation of the original doodly-squat, which first began appearing in print in the 1930s. This compound arose from the image of someone squatting and doodling on the ground beneath them -- as pretty a picture of time-wasting nonaccomplishment as anyone can imagine. The confusion of doodle with diddle "to fool around, dawdle" that led to diddly-squat is easily understood. But in the 1960s, this word took a turn for the worse: the association of squatting with defecation led to the unspeakable variation, diddly-s-t, containing a word US radio and TV networks are fined $300,000 for if it slips by their censors. This called for a euphemism which was simple enough: we just dropped the offensive word and, voilà: diddly.
In Play: Another interesting aspect of today's word is that, since it refers to something worthless or nothing at all, negating it has very little impact on its meaning: "Lionel Trane did diddly-squat while he was president of the Erie Railroad," means very nearly the same as, "Lionel Trane didn't do diddly-squat while he was president of the Erie Railroad." Nothing and next to nothing are not very far apart.