late 14c., as a term in logic and philosophy, from Old French posicion "position, supposition" (Modern French position), 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.)).
Meaning "proper place occupied by a person or thing" is from 1540s. Meaning "manner in which some physical thing is arranged or posed" first recorded 1703; specifically in reference to dance steps, 1778, sexual intercourse, 1883. Meaning "official station, employment" is from 1890.