eat one's hat

Example: “If he actually finishes that marathon, I'll eat my hat.”

Origin: In print by 1797, in Thomas Brydges's Homer Travestie, and popularized further by Charles Dickens's 1837 Pickwick Papers, where a character vows he'd "eat my hat and swallow the buckle whole" if proven wrong. Two folk explanations are commonly repeated for where the exact image came from, and neither survives close inspection: one credits King Charles II's unflattering nickname "Old Rowley," but the phrase isn't attested until well after his reign; the other points to a 15th-century savory pastry called a "hatte," but two centuries pass between the last recorded hatte and the phrase's actual appearance in print. Both theories have real chronological gaps, leaving the true origin of the specific hat image unresolved — the phrase's core function, an exaggerated declaration of certainty backed by an absurd, unappetizing penalty, needs no specific origin story to make sense on its own.