also protestor, 1540s, protestour, "one who makes solemn affirmation or declaration;" agent noun from protest (v.). From 1960 as "demonstrator against or public opponent of the established order."
Entries linking to protester
protest v.
mid-15c., protesten, "to declare or state formally or solemnly, bear witness or testimony to," from Old French protester and directly from Latin protestari "declare publicly, testify, protest" (see protest (n.)). Original sense preserved in to protest one's innocence. The meaning "make a solemn or formal declaration (often in writing) in condemnation of an act or measure, proposed or accomplished," is from c. 1600. The word's association with marches and rallies arose in 20c. Related: Protested; protesting.