*mr-trom which meant "killing", a noun derived from *mer- "to die".

Proto-Germanic, in fact, had two nouns derived from this word, later merging into the modern English noun: *murþra "death, killing, murder" (directly from Proto-Indo-European*mr-trom), whence Old English morðor "secret or unlawful killing of a person, murder; mortal sin, crime; punishment, torment, misery"; and *murþrijô "murderer; homicide" (from the verb *murþrijana "to murder"), giving