Green’s Dictionary of Slang

the penis; thus goose neck and giblets, the male genitals; have a bit of goose’s neck, to have sexual intercourse.

c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Goose Neck & Giblets. A Mans tackle. She longd for a Goose Neck and Giblets, for the Child carries the Mark, i.e. she is delivered of a Son.
1890–1904		Farmer & Henley Sl. and Its Analogues.