Bobbing for corn

The act of oral anal stimulation rimming; with reference to the discovery of undigested kernels of corn. Akin to bobbing for apples, but with scatological undertones. The phrase has its origins in the West Midlands.

Nick: Tom, you’ve got something stuck in your teeth.
Tom: Sorry yeah I’ve been bobbing for corn.
Nick: So I guess that’s not chocolate around your mouth.
Tom: No, Nick. It is not.