Green’s Dictionary of Slang

joe hep n.

also joe hip, joe hipp
[hep adj. (1)/hip adj. (1)]

(US) an aware, wise person.

[US]T.A. Dorgan in Zwilling TAD Lex. (1993) 45: Joe Hip/For Congress/Son of old man Hip.
[US]Berrey & Van Den Bark Amer. Thes. Sl. 352: Joe Hep, sharp cat, sharpy.
[US]D. Burley Orig. Hbk of Harlem Jive 15: Pop, I’m tops, replied Joe Hipp.