"a placing over against, opposite position," 1550s, from Late Latin contrapositionem (nominative contrapositio), noun of action from past-participle stem of contraponere "to place opposite, to oppose to," from contra "against" (see contra (prep., adv.)) + ponere "to put, place" (past participle positus; see position (n.)).
word-forming element making adjectives from verbs, meaning "pertaining to, tending to; doing, serving to do," in some cases from Old French -if, but usually directly from Latin adjectival suffix -ivus (source also of Italian and Spanish -ivo). In some words borrowed from French at an early date it has been reduced to -y (as in hasty, tardy).
<a href="https://www.etymonline.com/word/contrapositive">Etymology of contrapositive by etymonline</a>
Harper, D. (n.d.). Etymology of contrapositive. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/contrapositive