Green’s Dictionary of Slang

a piece of verbal punctuation, used as a form of intimacy, suggesting a complicity between addressee and addressed.

1825		H. Wilson Memoirs III 42: And your amiable daughters? Any of them married yet? Any of them thinking of it, hey?
1868		L.M. Alcott Little Women II 17: ‘I never cry unless from some great affliction.’ ‘Such as old fellows going to college, hey?’.
1887		‘’Arry on Ochre’ in Punch 15 Oct. 169/2: Save, hay, — out of two quid a week!
1946		J. O’Hara ‘Pilfrimage’ in New Yorker 9 Nov. 31/2: ‘You’re in town for this Donnybrook [i.e. a college football game] at the Stadium, hey? What do you do, cover all Notre Dame games?’ .
1979		E. Bond Worlds Part I iv: Hey up! old age P.
1998		(con. 1986) G. Pelecanos Sweet Forever 36: I’m older than you but, hey, I’m one of you.
1999		Guardian Guide 29 May–4 June 6: But, hey, I loved Men in Black.