Old English martyr, from Late Latin martyr, from Doric Greek martyr, earlier martys (genitive martyros) in Christian use "martyr," literally "witness," probably related to mermera "care, trouble," from mermairein "be anxious or thoughtful," from PIE *(s)mrtu- (cf. Sanskrit smarati "remember," Latin memor "mindful;" see memory).
Adopted directly into most Germanic languages, but Norse substituted native formation pislarvattr, literally "torture-witness." General sense of "constant sufferer" is from 1550s. Martyr complex "exaggerated desire for self-sacrifice" is attested from 1920.