Lewis & Short

suppŏsĭtĭo (subp-), ōnis, f. [suppono], a putting or setting under.

  1. * I. In gen.: ovorum, Col. 8, 5, 9.
  2. II. In partic., a putting in the place of another, substitution (of a child): pueri, Plaut. Capt. grex 3: puellae, id. Cist. 1, 3, 4: suppositionem facere, id. ib. 1, 2, 25; id. Truc. 2, 4, 83.