c.1315, "to assume as the basis of argument," from O.Fr.
supposer "to assume," probably a replacement of
*suppondre (influenced by O.Fr.
poser "put, place"), from L.
supponere "put or place under," from
sub "under" +
ponere "put, place" (see
position). Meaning "to admit as possible, to believe to be true" is from 1526.
Supposed "believed or thought to exist" is from 1582, often with the
-e- pronounced, to distinguish it from the passive p.t.
supposed, now common in the sense of "to have a duty or obligation" (1859).
Supposition (1410), as a term in logic is from L.L.
suppositionem (nom.
suppositio) "assumption, hypothesis," infl. by Gk.
hypothesis.