An Etymological Dictionary of Astronomy and Astrophysics

1. An expression or declaration of objection, disapproval, or dissent, often in opposition to something a person is powerless to prevent or avoid.
   

2. To give manifest expression to objection or disapproval; remonstrate (Dictionary.com).

Etymology (EN): M.E., from O.Fr. protest, from preotester, and directly from L. protestari “to declare publicly, protest,” from → pro- “forth, before” + testari “testify,” from testis “witness.”

Etymology (PE): Pâxos, literally “strike against,” from pâ-, contraction of pâd- “agianst,” → counter-,

• xos “to strike,” Gazi xos-, xus-, xûs- “to strike, throw;”
  Hamedani xostän, xus- “to throw”, Khunsari xus- “to strike, throw,” Kurd. (Sorani) xa-, (Kurmanji) xistin, xi- “to strike, beat,” Qohrudi xosta “to throw,” Ardestâni xoste, Shughni xust, xay-; Mid.Pers. xwas-, hws- “to trample;” Av. paiti xvanh- “to thresh;”
  Proto-Ir. *huah- “to strike, thresh” (Cheung 2007). ,