purchase (v.)
c.1300, "acquire, obtain; get, receive; procure, provide," also "accomplish or bring about; instigate; cause, contrive, plot; recruit, hire," from Anglo-French purchaser "go after," Old French porchacier "search for, procure; purchase; aim at, strive for, pursue eagerly" (11c., Modern French pourchasser), from pur- "forth" (possibly used here as an intensive prefix; see pur-) + Old French chacier "run after, to hunt, chase" (see chase (v.)).

Originally to obtain or receive as due in any way, including through merit or suffering; specific sense of "acquire for money, pay money for, buy" is from mid-14c., though the word continued to be used for "to get by conquest in war, obtain as booty" up to 17c. Related: Purchased; purchasing.
purchase (n.)
c.1300, purchas, "acquisition, gain;" also, "something acquired or received, a possession; property, goods;" especially "booty, spoil; goods gained by pillage or robbery" (to make purchase was "to seize by robbery"). Also "mercenary soldier, one who fights for booty." From Anglo-French purchace, Old French porchaz "acquisition, gain, profit; seizing, plunder; search pursuit, effort," from Anglo-French purchaser, Old French porchacier (see purchase (v.)).

From early 14c. as "endeavor, effort, exertion; instigation, contrivance;" late 14c. as "act of acquiring, procurement." Meaning "that which is bought" is from 1580s. The sense of "hold or position for advantageously applying power" (1711) is extended from the nautical verb meaning "to haul or draw (especially by mechanical power)," often used in reference to hauling up anchors, attested from 1560s. Wif of purchase (early 14c.) was a term for "concubine."