Green’s Dictionary of Slang

1. (US Und.) one who works the short-change racket.

1914		Jackson & Hellyer Vocab. Criminal Sl. 47: hyper [...] current amongst money-changers. A flim-flammer.
1931		Irwin Amer. Tramp and Und. Sl. 106: Hyper. – A ‘short change’ artist, one who habitually gives less than the proper change to a purchaser or customer.
1949		Monteleone Criminal Sl. (rev. edn) 118: hiper A swindler.
1950		Goldin et al. DAUL 96/1: Hiper. A short-change swindler or any petty confidence game operator.

2. (US black) a persuasive talker.

1943		D. Burley N.Y. Amsterdam News 9 Oct. 20: I’m a hyper who blows like a piper myself.
1944		D. Burley Orig. Hbk of Harlem Jive 17: .

3. a publicist.

1968

Sun. Times 11 Aug. 5: The activities of pop managers and professional ‘hypers’ have for a long time created doubts about the accuracy of the Top Thirty lists.