cuz when jack lost his face he made a design of his face and so he could see he but a lantern so yeah
See the link below, and scroll down to the stories about "Jack of the lantern".
Turnips
Cucumber
Turnips.
pumpkins
Because the worlds famous Jack O Lantern died and everybody puts the jack o lanterns in there window sell so that it reminds people about Jack O Lantern.
Actually jack-o-lanterns can be made out of any fruit or vegetable; it's just that pumpkins are large, and easy to hollow out and carve faces on.(It is believed that the first jack-o lanterns were made from turnips)
"Turnips" and sometimes potatoes.
A jack-o-lantern is a carved pumpkin, a pumpkin is just a plain vegetable.
Pumpkins
squash or gourds
Jack-o-Lanterns were originally made from turnips.