protestyoudaoicibaDictYouDict[protest 词源字典]
protest: [14] The noun protest comes from early modern French protest, a derivative of the verb protester, which goes back to Latin prōtestārī ‘make a public declaration’. This was a compound verb formed from the prefix prō- ‘out, in public’ and testārī ‘declare, bear witness’ (source of or related to English attest, contest, detest, testament, testify, etc).

The notion of ‘making an objection’ is a comparatively late development in the word’s semantic history. Protestant [16], which comes from the Latin present participle, originated in 1529 as a term for those Germans who dissented from the decree of the Diet of Spires, an assembly of the estates of the Holy Roman Empire, which called for obedience to Rome. It was first used in English in 1539, and within a few years had broadened out in application to denote anyone dissenting from Roman Catholicism.
=> attest, contest, detest, testament, testicle, testify[protest etymology, protest origin, 英语词源]
protest (n.)youdaoicibaDictYouDict
c. 1400, "avowal, pledge, solemn declaration," from Old French protest (Modern French prôtet), from preotester, and directly from Latin protestari "declare publicly, testify, protest," from pro- "forth, before" (see pro-) + testari "testify," from testis "witness" (see testament).

Meaning "statement of disapproval" first recorded 1751; adjectival sense of "expressing of dissent from, or rejection of, prevailing mores" is from 1953, in reference to U.S. civil rights movement. First record of protest march is from 1959.
protest (v.)youdaoicibaDictYouDict
mid-15c., "to declare or state formally or solemnly," from Old French protester, from Latin protestari "declare publicly, testify, protest" (see protest (n.)). Original sense preserved in to protest one's innocence. Related: Protested; protesting.