1:) To buckle up and do something: Gearing up (lit. Or fig.) and taking on a challenge or task with determination and readiness.
2:) To do the damn thing: Getting ready and fully committing to taking action, especially in the face of a difficult or demanding situation.
3:) A euphemism for male masturbation.
I don't care what you all say, I'm still going to skin the grizzly.