pectus
/ˈpɛktəs/noun
1 Anatomy and Medicine. The front of the thorax; the chest. In later use frequently attributive, especially in relation to congenital deformities of the chest.
2 Entomology. The lower surface of the thorax or prothorax of an insect or a spider.
Origin
Late 17th century; earliest use found in Blankaart's Physical Dictionary. From classical Latin pectus the breast, the chest, of unknown origin.