1610s, transitive, "to make a partner," from partner (n.). Intransitive sense, "join one another in partnership," is by 1961. Related: Partnered; partnering.

c. 1300, partiner, "a sharer or partaker in anything," altered from parcener (late 13c.), from Old French parçonier "partner, associate; joint owner, joint heir," from parçon "partition, division. portion, share, lot," from Latin partitionem (nominative partitio) "a sharing, partition, division, distribution" from past participle stem of partire "to part, divide" (from pars "a part, piece, a share," from PIE root *pere- (2) "to grant, allot").

The form in English has been influenced by part (n.). The word also may represent Old French part tenour "part holder." From late 14c. as "one who shares power or authority with another;" the commercial sense is by 1520s. Meaning "a husband or wife, one associated in marriage with another" is from 1749.

1570s, "state or condition of being a partner," from partner (n.) + -ship. In the commercial sense, "association of two or more persons for carrying on a business," from c. 1700.

"accomplice, companion," 1850, a dialectal shortening of pardner, pardener (1795), which represents a common pronunciation of partner (n.).

"desiring or having consensual intimate relations with more than one partner," by 1972, from poly- + amorous. Related: Polyamory.

early 15c., "partner" (a sense now obsolete), from Old French consort "colleague, partner," consorte "wife" (14c.), from Latin consortem (nominative consors) "partner, comrade; brother, sister," in Medieval Latin, "a wife," noun use of adjective meaning "having the same lot, of the same fortune," from assimilated form of com "with, together" (see con-) + sors "a share, lot" (from PIE root *ser- (2) "to line up").

Sense of "husband or wife" ("partner in marriage") is from 1630s in English. A prince consort (1837) is a prince who is the husband of a queen but himself has no royal authority (the most notable being Prince Albert of Saxe-Coburg and Gotha, husband of Queen Victoria; the initial proposal in Parliament in 1840 was to call him king-consort); queen consort is attested from 1667. Related: Consortial.

The husband of a reigning queen has no powers, he is not king unless an act of parliament makes him so. Philip of Spain, Mary's husband, bore the title of king, Anne's husband was simply Prince George of Denmark. Queen Victoria's husband was simply Prince Albert of Saxe-Coburg-Gotha until 1857 when the queen conferred on him the title of Prince Consort. [F.W. Maitland, "The Constitutional History of England," 1908]