Green’s Dictionary of Slang

(US) worthless; insignificant.

1967		Wentworth & Flexner DAS (Supplement).
1978		L.K. Truscott IV Dress Gray (1979) 197: It was diddlyshit rumors and such.
2002		Herod the Nut homepage 🌐 In future this page will serve as a voice for all my mad rantings. But for now you just have this diddly-shit introduction. Enjoy!!