Green’s Dictionary of Slang

1. (US drugs) an opium pipe [? the dipping of the yen hock under yen n.¹ into the bowl of the pipe prior to lighting the opium].

1949		Monteleone Criminal Sl. (rev. edn).
1953		Anslinger & Tompkins Traffic In Narcotics 307: dipper. An opium pipe.

2. the penis.

1980

W. Sherman Times Sq. 127: ‘I didn’t see you getting your dipper wet’ [HDAS].