Green’s Dictionary of Slang

gilligan (hitch) n.

also gilligan guzzler
[US naut. jargon gilligan hitch, an out-of-the-ordinary or speedily tied knot/guzzle n. (1); Ersine, Underworld and Prison Slang (1933), suggests ‘Mr. Gilligan, an old-time strong-arm actor’]

[1930s–50s] (US Und.) a stranglehold.