Nothing; anything at all (when used in negative statements). I have to admit that I know diddly-squat when it comes to computers.Unless you give me something in writing, that promise isn't worth diddly-squat.
diddly-squat
and (doodly-)squat (ˈdɪdliskwɑt and ˈdudliskwɑt)
n. nothing. (Folksy. Originally black or southern.) This contract isn’t worth diddly-squat.