unmarked (adj.)

prefix of negation, Old English un-, from Proto-Germanic *un- (source also of Old Saxon, Old Frisian, Old High German, German un-, Gothic un-, Dutch on-), from PIE *n- (source of Sanskrit a-, an- "not," Greek a-, an-, Old Irish an-, Latin in-), combining form of PIE root *ne- "not." Often euphemistic (such as untruth for "lie").

The most prolific of English prefixes, freely and widely used in Old English, where it forms more than 1,000 compounds. It underwent a mass extinction in early Middle English, but emerged with renewed vigor 16c. to form compounds with native and imported words. It disputes with Latin-derived cognate in- (1) the right to form the negation of certain words (indigestable/undigestable, etc.), and though both might be deployed in cooperation to indicate shades of meaning (unfamous/infamous), typically they are not.

It also makes words from phrases (such as uncalled-for, c. 1600; undreamed-of, 1630s; uncome-at-able, 1690s; unputdownable, 1947, of a book; un-in-one-breath-utterable, Ben Jonson; etc., but the habit is not restricted to un-; such as put-up-able-with, 1812). As a prefix in telegramese to replace not and save the cost of a word, it is attested by 1936.

"to put a mark on," Old English mearcian (West Saxon), merciga (Anglian) "to trace out boundaries;" in late Old English "make a mark or marks on," from Proto-Germanic *markojan (source also of Old Norse merkja, Old Saxon markon "appoint, observe, remark," Old Frisian merkia, Old High German marchon "to limit, plan out," German merken "to mark, note," Middle Dutch and Dutch merken "to set a mark on"), from the root of mark (n.1).

Influenced by the Scandinavian cognates. Meaning "to have a mark" is from c. 1400; that of "to notice, observe" is late 14c. Figurative sense of "designate as if by placing a mark on," hence "to destine," is from late Old English. Meaning "be a noteworthy feature of" is by 1660s. To mark time (1833) is from military drill, originally "move the feet as if marching but remain in place."

The verbs in Romanic are from the nouns, which are early borrowings from Germanic: Old French merchier "to mark, note, stamp, brand," French marquer "to mark," Spanish marcar, Italian marcare.