Merriam Webster says:
Main Entry: cal·zo·ne
Pronunciation: kal-'zOn, -'zO-nE, -'zO-nA; käl-'zo-nA
Function: noun
Inflected Form(s): plural calzone or calzones
Etymology: Italian, from calzone (singular of calzoni pants), augmentative of calza stocking, from Medieval Latin calcea, from Latin calceus shoe, from calc-, calx heel
Date: circa 1950
: a baked or fried turnover of pizza dough stuffed with various fillings usually including cheese