What were the original jack o’ lanterns made from?

Answer: Turnips (also mangel wurzels and possibly rutabagas)

Jack o’ lantern refers to a light that is sometimes seen in bogs or marshes. It was explained in Irish folklore as being Stingy Jack who avoided hell by tricking the devil but was denied entry into heaven due to his sins. He now has to wander the earth and lights his way with an ember from hell held within a turnip or rutabaga.