Green’s Dictionary of Slang

(orig. US teen) don’t worry, it’s all right etc.

1970		A. Young Snakes (1971) 44: ‘Ain’t no big thing,’ Champ said, winking at me in mock contempt.
1989		C. Hiaasen Skin Tight 98: I told you before, no big deal.
1995		D. Lodge Therapy (1996) 51: Hey, it’s no big deal, Tubby, I’m not in love with you or anything.
1997		Simon & Burns Corner (1998) 27: The night before, in fact, the knockers rolled past him on Fairmount. No big thing. It wasn’t like he was dirty when they came through.
2000		F. Kellerman Stalker (2001) 64: I ruffles some feathers. No big whoop. I’ll fix it. [Ibid.] 97: Guys’ll try. No big deal.
2000		F.X. Toole Rope Burns 18: I tout him on La Costa, but tell him it isn’t cheap, and he says no big thing.
2010		L. Berney Gutshot Straight [ebook] If doing that proved imposible, tough, no big wiggie.