"trace, impression," Old English mearc (West Saxon), merc (Mercian) "boundary, sign, limit, mark," from Proto-Germanic *marko (cf. Old Norse merki "boundary, sign," mörk "forest," which often marked a frontier; Old Frisian merke, Gothic marka "boundary, frontier," Dutch merk "mark, brand," German Mark "boundary, boundary land"), from PIE *merg- "edge, boundary, border" (cf. Latin margo "margin;" Avestan mareza- "border," Old Irish mruig, Irish bruig "borderland," Welsh bro "district").
The primary sense is probably "boundary," which had evolved by Old English through "sign of a boundary," through "sign in general," then to "impression or trace forming a sign." Meaning "any visible trace or impression" first recorded c.1200. Sense of "line drawn to indicate starting point of a race" (e.g. on your marks ...) first attested 1887. The Middle English sense of "target" (c.1200) is the notion in marksman and slang sense "victim of a swindle" (1883). The notion of "sign, token" is behind the meaning "numerical award given by a teacher" (1829). Influenced by Scandinavian cognates.
