The expression is a corruption of "umble pie," a tasty 13th century dish filled with spiced bits of animals' hearts, livers, kidneys and lungs. "Umble" derives from nomble, French for "deer innards."
The words "umble" and "humble" are in fact unrelated (the latter derives from the Latin word for "lowly"). But by the 19th century, "umble" had been dropped from the language and, because many Brits omit the spoken "h" at the beginning of words, the expression "umble pie" was mistakenly spelled "humble pie." People assumed the mysterious dish had something to do with humility.
Chew on that.
