Diddly squat, diddly bo squat, bo diddly squat
Meanings of "Diddly squat, diddly bo ..."
There are these three variations commonly used today. It can be interpreted two ways; either 'anything' or 'nothing' depending on the context. Nothing, an insignificant amount, is more prevalent in it's use. "Bo' is an intensifier like 'very' is for adjectives.
Also there is a guitarist named, Bo Diddley, (different spelling), and later there was a cartoon character named Bo Diddly Squat but that was after the expression was known.
If you say, "He knew diddly squat about baseball." That means he knew very little, or nothing of the game. If you say, "He didn't know diddly squat about baseball." That means he didn't know anything about the game. This is a slang expression.
Diddly Squat= Rien
Anglais: He did diddly squat during his vaction.
Français: Il n'a rien fait pendant ses vacances.