1842-43, Edgar Allan Poe, "The Mystery of Marie Roget"
“This thicket was a singular, an exceedingly singular one. It was unusually dense. Within its naturally walled enclosure were three extraordinary stones, forming a seat with a back and footstool.… , whose boys were in the habit of closely examining the shrubberies about them in search of the bark of the sassafras. Would it be a rash wager – a wager of one thousand to one – that a day never passed over the heads of these boys without finding at least one of them ensconced in the umbrageous hall, and enthroned upon its natural throne? Those who would hesitate at such a wager, have either never been boys themselves, or have forgotten the boyish nature."
The subject of a bet.
(law) A contract by which two parties or more agree that a certain sum of money, or other thing, shall be paid or delivered to one of them, on the happening or not happening of an uncertain event.
(law) An offer to make oath.
verb
(transitive) To bet something; to put it up as collateral.
I'd wager my boots on it.
(intransitive, figuratively) To suppose; to dare say.
I'll wager that Johnson knows something about all this.