marker (n.)

Old English mearcere "writer, notary" (glossing Latin notarius "clerk"), literally "one who marks," agent noun from mark (v.). Not found again until late 15c., hence modern use is perhaps a separate formation. Meaning "monument stone" is from 1888. Sense of "took for marking" is by 1725; meaning "felt-tipped marker pen" is from 1951, so called because their purpose was to highlight text.