surplice (n.)

"loose white robe," c. 1200, from Old French surpeliz (12c.), from Medieval Latin superpellicium (vestmentum) "a surplice," literally "an over fur (garment)," from Latin super "over" (see super-) + Medieval Latin pellicium "fur garment, tunic of skins," from Latin pellis "skin" (from PIE root *pel- (3) "skin, hide"). So called because it was donned over fur garments worn by clergymen for warmth in unheated medieval churches.