plastron

English speakers first borrowed French's word for a breastplate, plastron, as the name for the protective plate worn under a tunic of [chain mail](/dictionary/chain mail) by knights. In the 17th century, plastron was extended to the pad used to protect the torso of a fencer. Two centuries later, herpetologists appropriated the word for a slightly different type of protection: the underside of a turtle's shell, which consists typically of nine bones overlaid by horny plates. That was followed by the word's application in the world of fashion to coverings that adorn the front of a woman's bodice, such as a lacy bib, as well as to a man's separate or detachable starched shirtfront (which is typically worn under a jacket).