Turnip Jack-o'-Lanterns Are the Root of All Evil -...

According to English Heritage, which manages over 400 of England's historic buildings, monuments and sites, jack-o'-lanterns originated in Ireland, "where people have been carving turnips and other root vegetables for centuries, to ward off evil spirits." Irish legend holds there was an actual man named Jack, who was "cursed to spend all of time roaming the earth with only a burning coal (inside a carved out turnip) to light the way, as his punishment for trying to trick the devil."

A few hundred years ago, this story apparently induced people all over the British Isles to carve faces into their root veggies during the annual autumnal decorative gourd season. Turnips—sturdy; dependable; abundant—were the canvas of choice, but people also carved beets and potatoes in order to ward off wandering Jack and others who might bear them ill will.

 

https://www.atlasobscura.com/articles/turnip-jack-o-lanterns-are-the-root-of-all-evil