proprietary adj.

c. 1300, properte, "nature, quality, distinctive character always present in an individual or class," later "possession, land or goods owned, things subject to ownership" (early 14c., but this sense is rare before 17c.), from an Anglo-French modification of Old French proprete, "individuality, peculiarity; property" (12c., Modern French propreté) and directly from Latin proprietatem (nominative proprietas) "ownership, a property, propriety, quality," literally "special character" (a loan-translation of Greek idioma), noun of quality from proprius "one's own, special" (see proper). Compare propriety, which is another form of the same French word.

For "possessions, private property" Middle English sometimes used proper goods. Hot property "sensation, a success" is from 1947 in stories in Billboard magazine.

1630s, "owner, by royal grant, of an American colony," probably from proprietary (n.) in this sense. OED describes it as "Anomalously formed and substituted in 17th c. for the etymological word PROPRIETARY." In the general sense of "one who holds something as property, one who has the legal right or exclusive title" to something, it is attested from 1640s. Related: Proprietorship.