bet (one's) bottom dollar

To be totally certain that something will happen or prove true (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 on it raining tomorrow! I bet my bottom dollar that Kevin will be late tonight—he's never on time! Well, we know the rest of the family has gotten to town, so if Mom's calling you repeatedly, I'd bet my bottom dollar they're making her miserable.

bet your bottom dollar

If you say that you bet your bottom dollar that something will happen or is true, you mean that you are certain that it will happen or that it is true. A police insider was quoted as saying of the crime: `You can bet your bottom dollar Sinclair was involved'. He hasn't passed us and we haven't passed him, but I'd bet my bottom dollar he's around somewhere. Note: This expression refers to the piles of coins on a poker (= gambling game) table. A confident player would bet by pushing a pile of coins to the centre of the table using the bottom dollar, on which all the others were resting.

bet your bottom dollar

Risk your all your assets. “Bottom dollar” was the last amount of money in a gambling game stake. If you lost it, you were flat-out broke. Therefore, someone who said that you could bet your bottom dollar on something was telling you that it was a certainty. And sometimes it was.