mid-12c., "large group of people," from Old French compagnie "society, friendship, intimacy; body of soldiers" (12c.), from Late Latin companio, literally "bread fellow, messmate," from Latin com "with, together" (see com-) + panis "bread," from PIE root *pa- "to feed." Abbreviation co. dates from 1670s. 

Meaning "companionship, consort of persons one with another, intimate association" is from late 13c. Meaning "person or persons associated with another in any way" is from c. 1300. In Middle English the word also could mean "sexual union, intercourse" (c. 1300).

From late 14c. as "a number of persons united to perform or carry out anything jointly," which developed a commercial sense of "business association" by 1550s, the word having been used in reference to trade guilds from late 14c. Meaning "subdivision of an infantry regiment" (in 19c. usually 60 to 100 men, commanded by a captain) is from c. 1400. 

Meaning "person or persons with whom one voluntarily associates" is from c. 1600; phrase keep company "consort" is from 1560s (bear company in the same sense is from c. 1300). Expression two's company "two persons are just right" (for conversation, etc.), is attested from 1849; the following line varies: but three is none (or not), 1849; three's trumpery (1864); three's a crowd (1856). 

c. 1300, "wheeled vehicle," from Anglo-French carre, Old North French carre, from Vulgar Latin *carra, related to Latin carrum, carrus (plural carra), originally "two-wheeled Celtic war chariot," from Gaulish karros, a Celtic word (compare Old Irish and Welsh carr "cart, wagon," Breton karr "chariot"), from PIE *krsos, from root *kers- "to run." The Celtic-Latin word also made it into Greek, as karron "wagon with four wheels."

"From 16th to 19th c. chiefly poetic, with associations of dignity, solemnity, or splendour ..." [OED]. Used in U.S. by 1826 of railway freight carriages and of passenger coaches on a railway by 1830; by 1862 of streetcars or tramway cars. The extension to "automobile" is by 1896, but between 1831 to the first decade of 20c. the cars meant "railroad train." Car bomb is attested from 1972, in a Northern Ireland context. The Latin word also is the source of Italian and Spanish carro, French char.

also carwash, by 1924, "act of washing an automobile," also "commercial establishment where an automobile can be washed," from car (n.) + wash (n.).

1846 in railroading sense, from hand (n.) + car.

1839 in railroading, from flat (adj.) + car (n.).

"car on a cable railroad," 1879, from cable (n.) + car. A streetcar moved by an endless cable which is cased in a small tunnel under the railway and kept in motion by a remote stationary engine.

racing car with a basic chassis of an ordinary commercially produced vehicle, 1914, American English, from stock (n.2) + car. Earlier "a railroad car used to transport livestock" (1858).

1863, from horse (n.) + car (n.).

"place for parking automobiles," 1926, British English, from car (n.) + park (n.).

Oh the torn up ticket stubs

From a hundred thousand mugs

Now washed away with dead dreams in the rain;

And the car-park's going up

And they're pulling down the pubs

And it's just another bloody rainy day

[The Pogues, "White City," 1989]

also carpool, "the sharing of a car ride by more than one person going to the same destination," 1942, American English, from car + pool (n.2). As a verb from 1962. Related: Carpooled; carpooling.