pot-pie (n.)

"deep, circular vessel," from late Old English pott and Old French pot "pot, container, mortar" (also in erotic senses), both from a general Low Germanic (Old Frisian pott, Middle Dutch pot) and Romanic word from Vulgar Latin *pottus, which is of uncertain origin, said by Barnhart and OED to be unconnected to Late Latin potus "drinking cup." Similar Celtic words are said to be borrowed from English and French.

Specifically as a drinking vessel from Middle English. Slang meaning "large sum of money staked on a bet" is attested from 1823; that of "aggregate stakes in a card game" is from 1847, American English.

Pot roast "meat (generally beef) cooked in a pot with little water and allowed to become brown, as if roasted," is from 1881. Pot-plant is by 1816 as "plant grown in a pot." The phrase go to pot "be ruined or wasted" (16c.) suggests cooking, perhaps meat cut up for the pot. In phrases, the pot calls the kettle black-arse (said of one who blames another for what he himself is also guilty of) is from c. 1700; shit or get off the pot is traced by Partridge to Canadian armed forces in World War II. To keep the pot boiling "provide the necessities of life" is from 1650s.

c. 1300 (probably older; piehus "bakery" is attested from late 12c.), "baked dish of pastry filled with a preparation of meats, spices, etc., covered with a thick layer of pastry and baked," from Medieval Latin pie "meat or fish enclosed in pastry" (c. 1300), which is perhaps related to Medieval Latin pia "pie, pastry," also possibly connected with pica "magpie" (see pie (n.2)) on notion of the bird's habit of collecting miscellaneous objects.

According to the OED, the word is not known outside English with the exception of Gaelic pighe, which is from English. In the Middle Ages, a pie had many ingredients, a pastry but one. Fruit pies began to appear c. 1600.

The word in the figurative sense of "something easy" is from 1889; the earlier expression easy as eating pie is by 1884. Slice of the pie in the figurative sense of "something to be shared out" is by 1967. Pie-eyed "drunk" is from 1904. Phrase pie in the sky is attested by 1911, from Joe Hill's Wobbly parody of hymns. Pieman "baker or seller of pies" is by c. 1300 as a surname. Pie chart is from 1922.