Is it ensure, insure, or assure?
1650s, from Latin corium "skin, hide, leather," related to cortex "bark," scortum "skin, hide," from PIE root *(s)ker- (1) "to cut" (cf. Sanskrit krtih "hide;" Old Church Slavonic scora "skin," Russian skora "hide," kora "bark;" Welsh corwg "boat made with leather skins;" Old English sceran "to cut, shear;" see shear (v.)). Related: Coriaceous.
corium co·ri·um (kôr'ē-əm)
n. pl. co·ri·a (kôr'ē-ə)
the thicker, deeper layer of the skin underlying the epidermis and made up of connective tissue. It is present in varying degrees of development among various vertebrate groups, being relatively thin and simple in aquatic animals and progressively thicker and more complex in terrestrial species