(from Online Etymology Dictionary)
(v.1) ”put in a certain position,” late 14c., “suggest, propose, suppose, assume,” from O.Fr. poser ”put, place, propose,” a term in debating, from L.L. pausare ”to halt, rest, pause” (see pause). The O.Fr. verb acquired the sense of L. ponere ”to put, place,” by confusion of the similar stems. Sense of “to assume a certain attitude” is from 1850; the trans. sense (as an artist’s model, etc.) is from 1859. The noun meaning “act of posing the body” is from 1818; its sense of “attitudinize” is from 1840.pose
(v.2) ”to puzzle, confuse, perplex,” 1590s, earlier “question, interrogate” (1520s), probably from M.Fr. poser ”suppose, assume,” from O.Fr.poser (see pose (v.1)). Also in some cases a shortening of English appose ”examine closely,” and oppose.