means a baked dish of fruit, meat, or other filling enclosed in or topped by pastry.

from English from the Middle Ages, and the word's likeliest backstory is delightfully odd: it's thought to come from 'magpie,' the bird (once just called a 'pie'). The reasoning? A magpie hoards a jumble of odd bits, and early pies were a similar mishmash of varied ingredients tucked under one crust. It's a plausible folk-linked theory rather than a sealed case — the bird-name connection is widely accepted but not absolutely proven.