"Opposition parties EAT HUMBLE PIE. Republican Party candidate Mr Trump emerged victorious against the odds in results announced yesterday, as he defeated Mrs Clinton."
- To be forced to acknowledge one's deficiencies or errors.
(The New Dictionary of Cultural Literacy, Third Edition.)
--- WORD ORIGIN
This expression derives from umble pie (without the H), which was a pie filled with liver, heart and other internal organs, especially of cow but often deer. These parts were known as umbles, and since they were considered inferior food, in medieval times the pie was often served to lower-class people.
Although umbles and the modern word humble (the verb form to humble means to destroy the pride of someone or cause someone to be modest in spirit) are etymologically unrelated, each word has appeared both with and without the initial "H" after the Middle Ages until the 19th century.
(adapted from Wikipedia)
BTW, Another common phrase using "pie" is
- to have a finger in the pie = die Hand im Spiel haben