contractyoudaoicibaDictYouDict[contract 词源字典]
contract: [14] English acquired the word contract in stages, although in all cases the ultimate source was contractus, the past participle of Latin contrahere, a compound verb formed from the prefix com- ‘together’ and trahere ‘pull, draw’ (source of English traction and tractor). This meant literally ‘pull together’, but it had a variety of metaphorical senses, including ‘bring about’ and ‘enter into an agreement’, and it was the latter which first passed into English via Old French as a noun meaning ‘mutual agreement’.

The arrival of the verb contract did not happen until the 16th century; it developed from an earlier adjective contract, which came again from Old French contract. This introduced a further sense of Latin contrahere; ‘become narrowed, get smaller’.
=> distract, retract, traction, tractor[contract etymology, contract origin, 英语词源]
contract (v.)youdaoicibaDictYouDict
late 14c., "make narrow, draw together;" early 15c. "make an agreement;" from Middle French contracter, from Latin contractus, past participle of contrahere "to draw together, combine, make an agreement" (see contract (n.)). Related: Contracted; contracting.
contract (n.)youdaoicibaDictYouDict
early 14c., from Old French contract (Modern French contrat), from Latin contractus "a contract, agreement," from past participle of contrahere "to draw together," metaphorically, "to make a bargain," from com- "together" (see com-) + trahere "to draw" (see tract (n.1)). U.S. underworld sense of "arrangement to kill someone" first recorded 1940.