"I'll eat my hat" is something people say when they are very sure that something will not happen. They mean that if it does happen, they would be so surprised that they would do something silly or impossible, like eating their hat.
People use this expression to show strong confidence in their opinion or prediction. It is usually said in a joking or dramatic way, not as a serious promise.
People use this expression to show strong confidence in their opinion or prediction. It is usually said in a joking or dramatic way, not as a serious promise.
If that old car starts on the first try tomorrow morning, I'll eat my hat.