"put to death as punishment for adherence to some religious belief (especially Christianity)," Middle English martiren, from Old French martiriier and in part from Old English gemartyrian, from martyr (n.). Middle English also had a verb martyrize (mid-15c.).
"one who bears testimony to faith," especially "one who willingly suffers death rather than surrender his or her religious faith," specifically "one of the Christians who in former times were put to death because they would not renounce their beliefs," late Old English martyr, from Late Latin martyr, (source also of Old French martir, Spanish martir, Italian martire, etc.), from Doric Greek martyr, earlier martys (genitive martyros), in Christian use "martyr," literally "witness."
This Greek word is sometimes said to be related to mermera "care, trouble," from mermairein "be anxious or thoughtful," from PIE *(s)mrtu- (source also of Sanskrit smarati "remember," Latin memor "mindful"), however Beekes has phonetic objections to this and suggests it is rather a loan-word from Pre-Greek. For sense shift from abstract "testimony" to "a witness," compare French témoin "witness" from Latin testimonium; English witness (n.) "one who testifies," originally "testimony."
The word was adopted directly into most Germanic languages (Old Saxon, Old Frisian martir, Old High German martyr, etc.), but Norse used a native formation pislarvattr, literally "torture-witness." Meaning "one who suffers death or grievous loss in defense or on behalf of any belief or cause" (love, etc.) is from late 14c. General sense of "constant sufferer, a victim of misfortune, calamity, disease, etc.," is from 1550s. Martyr complex "exaggerated desire for self-sacrifice" is attested by 1916.
"history of the lives, sufferings, and deaths of Christian martyrs," 1590s, a native formation from martyr (n.) + -ology, or else from Church Latin martyrologium, from Ecclesiastical Greek martyrologicon. Especially, in the Catholic Church, "a list or calendar of martyrs, arranged according to their anniversaries." Middle English had martiloge "the register of martyred saints" (late 14c.), from Medieval Latin martilogium. Related: Martyrological.
masc. proper name, from French, shortened from Latin Vincentius, from vincentem (nominative vincens) "conquering," from vincere "to overcome" (from nasalized form of PIE root *weik- (3) "to fight, conquer"). The name of a 3c. martyr, it was introduced in England c. 1200.
c. 1300, diademe, "aureole of a martyr or confessor;" mid-14c., "a crown, anything worn on the head as a mark of royalty," from Old French diademe and directly from Latin diadema "cloth band worn around the head as a sign of royalty," from Greek diadema "the headband worn by Persian kings and adopted by Alexander the Great and his successors," from diadein "to bind across," from dia "across" or "through" (see dia-) + dein "to bind," which is related to desmos "band," from PIE root *dē- "to bind." Related: Diademed.