Birthmark is a compound of birth (from Old Norse byrðr / Old English gebyrd) + mark (Old English mearc 'boundary, sign'). The historical trail runs through byrðr in Old Norse and mearc in Old English. Morphologically, birthmark is transparent: it is a compound of birth (from Old Norse byrðr / Old English gebyrd) + mark (Old English mearc 'boundary, sign'). Used as a noun, birthmark now means "a permanent colored mark on the skin present from birth", so the present definition can be read against the older forms and meanings. The same lexical family is also visible in related forms such as birth and mark. The result is a borrowed or transmitted form whose modern spelling carries a compact record of its route into English.