Green’s Dictionary of Slang

1. the penis [cf. arse-opener under arse n.].

1890–1904		Farmer & Henley Sl. and Its Analogues.
1896		Farmer Vocabula Amatoria (1966) 43: Bougeoir (le). The penis; ‘the eye-opener’.

2. (US Und.) a tramp who has homosexual sex with a young companion.

1927		‘Jargon of the Und.’ in DN V x 445: Eye opener, A pederast.
1931		Irwin Amer. Tramp and Und. Sl. 70: Eye Opener [...] A pederast.
1949		Monteleone Criminal Sl. (rev. edn).
1972		(con. 1930s–40s) B. Rodgers Queens’ Vernacular 107: Hobo slang (kwn ’30s & ’40s) [...] The tramp who fucked his boy was known as a bunker and eye-opener.