contestyoudaoicibaDictYouDict[contest 词源字典]
contest: [16] The idea underlying contest, unlikely as it may seem, is of ‘bearing witness’. It goes back to Latin contestārī, a compound verb formed from the prefix com- ‘together’ and testārī ‘bear witness’, which in turn was derived from testis ‘witness’ (whence English testament, testicle, and testimony). This verb signified the bringing of a lawsuit by ‘calling witnesses together’ from both sides.

Hence was introduced the adversarial or competitive notion that passed into English, probably via Old French contester (although in the 16th and 17th centuries traces of the original Latin sense ‘bear joint witness, attest’ survived in English, presumably as a scholarly reintroduction).
=> testament, testicle, testimony[contest etymology, contest origin, 英语词源]
contest (v.)youdaoicibaDictYouDict
c. 1600, from French contester "dispute, oppose," from Middle French, from Latin contestari (litem) "to call to witness, bring action," from com- "together" (see com-) + testari "to bear witness," from testis "a witness," (see testament). Calling witnesses as the first step in a legal combat. Related: Contestable; contested; contesting.
contest (n.)youdaoicibaDictYouDict
1640s, from contest (v.).