1520s, "opposition, contrast," originally in rhetoric, "the bringing of contrary ideas or terms in close opposition;" 1530s as "that which is in (rhetorical) opposition or contrast," from Late Latin antithesis, from Greek antithesis "opposition, resistance," literally "a placing against," also a term in logic and rhetoric, noun of action from antitithenai "to set against, oppose," a term in logic, from anti "against" (see anti-) + tithenai "to put, place" (from reduplicated form of PIE root *dhe- "to set, put").
The extended sense of "direct or striking opposition" is from 1630s; by 1831 as "that which is the direct opposite."
<a href="https://www.etymonline.com/word/antitheses">Etymology of antitheses by etymonline</a>
Harper, D. (n.d.). Etymology of antitheses. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/antitheses