bet bottom dollar

bet your bottom dollar

Be certain that something will happen (so much so that one would hypothetically risk one's last dollar betting on it). I lost my umbrella, so you can bet your bottom dollar that it will rain tomorrow! Oh, you can bet your bottom dollar that Kevin will be late tonight—he's never on time!
See also: bet, bottom, dollar
Farlex Dictionary of Idioms.

bet one's bottom dollar

 and bet one's life
Fig. to be quite certain (about something). (A bottom dollar is the last dollar.) I'll be there. You bet your bottom dollar. I bet my bottom dollar you can't swim across the pool. You bet your life I can't swim that far.
See also: bet, bottom, dollar
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • bet one’s bottom dollar
  • bet your bottom dollar
  • bet your bottom dollar/your life
  • you can bet your bottom dollar (on something)
  • you bet your bottom
  • (one's) bottom dollar
  • bet on it
  • bet on
  • bet on (someone or something)
  • a long shot