chucking the monkey

Pitched at a GTLive Stream during a playthrough of Little Nightmares. Though no explicit definition was given, context provided by MatPat and Steph suggests it is a euphemism for masturbation. Repeated remarks about both of them chucking their monkeys warranted a mature stream warning. They talked about not chukcing the monkey in front of an audience and equal chucking the monkey rights.

Person 1: Ugh I'm so stressed right now.
Person 2: Try putting on some porn and chucking the monkey. It always helps me relax.