parapet (n.)

1580s, "wall or rampart rising breast-high," from Middle French parapet "breastwork" (16c.), or directly from Italian parapetto, from para- "defense" (see para- (2)) + petto "breast," from Latin pectus (see pectoral (adj.)). Meaning "low wall at the edge of a structure to keep people from falling off" is from 1590s.