Green’s Dictionary of Slang

(US teen) a general excl. implying ‘without question!’.

1992		Lord Finesse ‘O Lord’ 🎵 No diggity, one time like that.
1997–2000		College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 No dig (no diggity) (interjection) That’s true.
1997–2001		Online Sl. Dict. 🌐 no diggity 1. used as an agreement. Note: may or may not be paired with another phrase. (‘No diggity, Einstein was smart!’ or simply ‘No diggity!’).
2002		‘Touré’ Portable Promised Land (ms.) 160: We Words (My Favorite Things) [...] No diggity. Bomb diggity.
2012		Danny! ‘Go That-A-Way’ 🎵 No diggity, I already know I’m the shit, you illiterate son of a bitch.