eat humble pie
The spoken phrase a numble pie (a pie made from the entrails of a deer) was re-interpreted as an umble pie, then written as (a) humble pie, whereafter the figurative meaning developing.
- (idiomatic, intransitive) to admit one's faults; to make a humiliating apology
1869, Louisa May Alcott, An Old-Fashioned Girl:
- Polly had a spice of girlish malice, and rather liked to see domineering Tom eat humble-pie, just enough to do him good, you know.
to admit one's faults