you (can) bet your boots

You can be absolutely certain that something will happen. (Sometimes used ironically. You bet your boots I'm going to that concert—I've been saving up for my ticket for months now! Oh, you can bet your boots that Kevin will be late tonight—he's never on time! I lost my umbrella, so you can bet your boots that it's going to rain soon.

you can bet your boots (or bottom dollar or life)

you may be absolutely certain. informal

You bet your boots!

exclam. You can be absolutely certain! Am I happy? You bet your boots!