The verb form of juxtaposition is juxtapose, as in "the author juxtaposed the protagonist's dirty, ragged clothes with the spotless interior of the wealthy villain's mansion." The word juxtaposition comes from the Latin juxta meaning "next" and the French poser meaning "to place."

"the act of placing or the state of being placed in nearness or contiguity," 1660s, from French juxtaposition (17c.), from Latin iuxta "beside, very near, close to, near at hand" + French position (see position (n.)).

Etymologists believe juxtapose is a back-formation that was created when people trimmed down the noun juxtaposition. Historical evidence supports the idea: juxtaposition shows up in the 17th century and juxtapose in the 19th.