suppose v.

word-forming element meaning "under, beneath; behind; from under; resulting from further division," from Latin preposition sub "under, below, beneath, at the foot of," also "close to, up to, towards;" of time, "within, during;" figuratively "subject to, in the power of;" also "a little, somewhat" (as in sub-horridus "somewhat rough"), from PIE *(s)up- (perhaps representing *ex-upo-), a variant form of the root *upo "under," also "up from under." The Latin word also was used as a prefix and in various combinations.

In Latin assimilated to following -c-, -f-, -g-, -p-, and often -r- and -m-. In Old French the prefix appears in the full Latin form only "in learned adoptions of old Latin compounds" [OED], and in popular use it was represented by sous-, sou-; as in French souvenir from Latin subvenire, souscrire (Old French souzescrire) from subscribere, etc.

The original meaning is now obscured in many words from Latin (suggest, suspect, subject, etc.). The prefix is active in Modern English, sometimes meaning "subordinate" (as in subcontractor); "inferior" (17c., as in subhuman); "smaller" (18c.); "a part or division of" (c. 1800, as in subcontinent).

late 14c., posicioun, as a term in logic and philosophy, "statement of belief, the laying down of a proposition or thesis," from Old French posicion "position, supposition" (Modern French position) and directly from Latin positionem (nominative positio) "act or fact of placing, situation, position, affirmation," noun of state from past-participle stem of ponere "put, place." Watkins tentatively identifies this as from PIE *po-s(i)nere, from *apo- "off, away" (see apo-) + *sinere "to leave, let" (see site). But de Vaan identifies it as from Proto-Italic *posine-, from PIE *tkine- "to build, live," from root *tkei- "to settle, dwell, be home" (see home (n.)).

The meaning "place occupied by a person or thing" especially a proper or appropriate place, is from 1540s; hence "status, standing, social rank" (1832); "official station, employment" (1890). The meaning "manner in which some physical thing is arranged or posed, aggregate of the spatial relations of a body or figure to other such bodies or figures" is recorded by 1703; specifically in reference to dance steps, 1778, to sexual intercourse, 1883. Military sense of "place occupied or to be occupied" is by 1781.