Green’s Dictionary of Slang

1. (US tramp) one who poses as a deaf mute or deaf and dumb.

1929		V.W. Saul ‘Vocab. of Bums’ in AS IV:5 339: Dee Dee—Deaf and dumb; or someone faking to be deaf and dumb.
1931		Irwin Amer. Tramp and Und. Sl. 61: Dee Dee. – A deaf mute, or one feigning the affliction.
1949		Monteleone Criminal Sl. (rev. edn).

2. (UK drugs) a drug dealer.

1997

N. Barlay Curvy Lovebox 28: Deedees’re always paranoid about everythin’.