Nah gammon - A stupid way to say you're not going to do something, like y

A stupid way to say you're not going to do something, like you're too dumb to know what you're doing.

Nah gammon, I’m not going to school. (He skipped for a week.)

Nah gammon, I’m not doing my project. (He got a zero.)

Nah gammon, I’m not talking to my mom. (He texted her 20 times.)