​MURDER, in law, the unlawful killing of a person with malice aforethought (see Homicide). The O. Eng. morðor comes ultimately from the Indo-European root mar–, to die, which has also given Lat. mors, death, and all its derivatives in English, French and other Rom. languages; cf. Gr. βροτός, for μορτός, mortal. The O. Eng. form, Latinized as murdrum, murtrum, whence Fr. meurtre, is represented in other Teutonic languages by a cognate form, e.g. Ger. Mord, Du. moord.