Meaning

noun one who suffers for the sake of principle

noun one who voluntarily suffers death as the penalty for refusing to renounce their religion

verb kill as a martyr

originFrom Middle English martir, from Old English martyr, itself a borrowing from Ecclesiastical Latin martyr, from Ancient Greek μάρτυρ (mártur), later form of μάρτυς (mártus, “witness”).

Etymology from Wiktionary, CC BY-SA 3.0