...non potestis Deo servire et mamonae
• jack-o'-lantern •
Pronunciation: jæk-ê-læn-têrn • Hear it!
Part of Speech: Noun
Meaning: A lantern made from a hollowed pumpkin with openings representing eyes, nose, and mouth to make it look like a face—a symbol of Halloween.
Notes: No, the symbol of Halloween in North America does not come from a heavy drinking but stingy Irishman by the name of Jack O'Lantern, though it is a fetching story. It is the reduction of an old phrase, "jack with a lantern," spelled in a peculiar way. It is currently used as a single noun, so the plural is jack-o'-lanterns.
In Play: The custom of putting carved vegetables out on Halloween did originate with the Catholic Irish. The Irish once placed carved turnips and rutabagas with candles inside in their windows to ward off the dead souls they presumed wandered about on the eve of All Saints Day, so-called Hallow E'en "Holy Evening". They switched to pumpkins when they emigrated to America.
Word History: Jack-with-a-lantern originally meant simply "man with a lantern" (jack, as in the phrase, "every man, jack of them"), and referred to night watchmen. Its structure is analogical with that of "will-o'-the-wisp", which originally meant only "a man named Will with a wisp (whiskbroom)". Both "will-o'-the-wisp" and "jack-o'-lantern" later were used to refer to what the Romans called ignis fatuus "crazy fire," the pale mysterious fire of swamp gases burning over marshy areas. Will-o'-the-wisp was presumed to be a sprite carrying a wisp of a torch across the swamps. Jack-o'-lantern was assumed to be a man with a lantern. (Please see the correction below.)