Old English cros "instrument of Christ's crucifixion; symbol of Christianity" (mid-10c.), probably from Old Norse or another Scandinavian source, picked up by the Norse from Old Irish cros, from Latin crux (accusative crucem, genitive crucis) "stake, cross" on which criminals were impaled or hanged (originally a tall, round pole); hence, figuratively, "torture, trouble, misery;" see crux. Also from Latin crux are Italian croce, French croix, Spanish and Portuguese cruz, Dutch kruis, German Kreuz.
The modern word is the northern England form and has predominated. Middle English also had two other forms of the same word, arriving from the continent by different paths: cruche, crouche (c. 1200) was from Medieval Latin, with pronunciation as in Italian croce (compare Crouchmas "festival of the Invention of the Cross," late 14c.). Later, especially in southern England, the form crois, croice, from Old French, was the common one (compare croisade, the older form of crusade). The Old English word was rood.
By c. 1200 as "ornamental likeness of the cross, something resembling or in the form of a cross; sign of the cross made with the right hand or with fingers." From mid-14c. as "small cross with a human figure attached; a crucifix;" late 14c. as "outdoor structure or monument in the form of a cross." Also late 14c. as "a cross formed by two lines drawn or cut on a surface; two lines intersecting at right angles; the shape of a cross without regard to religious signification." From late 12c. as a surname.
From c. 1200 in English in the figurative sense "the burden of a Christian; any suffering voluntarily borne for Christ's sake; a trial or affliction; penance in Christ's name," from Matthew x.38, xvi.24, etc. Theological sense "crucifixion and death of Christ as a necessary part of his mission" is from late 14c.
As "a mixing of breeds in the production of animals" from 1760, hence broadly "a mixture of the characteristics of two different things" (1796). In pugilism, 1906, from the motion of the blow, crossing over the opponent's lead (1880s as a verb; cross-counter (n.) is from 1883). As "accidental contact of two wires belonging to different circuits," 1870.