Yay. Nothing like carving pumpkins and turning them into jack-o-lanterns.
Students from my ESOL (English for speakers of other languages) conversation class managed to stump me. They asked why we call them jack-o-lanterns, and I had to answer, "I don't know." The best answer Wikipedia gives is the origin from the latin phrase ignis fatuus which is sometimes translated "will-o'-wisp, corpse candle, jack-o'-lantern, friar's lantern, gunderslislik, and wisp, a Folklore depiction of ghostly light sometimes seen at night or twilight over bogs, swamps, and marshes." Meh. That hardly helps. And the History channel will tell you a folk tale, but I think the common thread is that we don't know.
So why are you called jack-o-lanterns, scary glowing pumpkin faces?