means A pen with a felt or porous tip that lays down a thick line of ink, used for writing, drawing, or labeling on paper, whiteboards, and most surfaces it shouldn't touch.

from From "mark" plus the agent suffix "-er" — literally "a thing that marks." "Mark" descends from Old English "mearc," meaning a boundary, sign, or border, a word with deep Germanic roots (a cousin of the "march" in borderlands like the Welsh Marches). For centuries a marker was anything that made or showed a mark — a boundary stone, a token, a bookmark. The specific sense of a fat-tipped ink pen is a 20th-century arrival, riding in on the felt-tip and its descendants.