unreal 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.

early 14c., "actually existing, having physical existence (not imaginary);" mid-15c., "relating to things" (especially property), from Old French reel "real, actual," from Late Latin realis "actual," in Medieval Latin "belonging to the thing itself," from Latin res "property, goods, matter, thing, affair," which de Vaan traces to a PIE *Hreh-i- "wealth, goods," source also of Sanskrit rayim, rayah "property, goods," Avestan raii-i- "wealth."

The meaning "genuine" is recorded from 1550s; the sense of "unaffected, no-nonsense" is from 1847. Real estate, the exact term, "land, including what is naturally or artificially on or in it" is recorded from 1660s, but as far back as Middle English real was used in law in reference to immovable property, paired with, and distinguished from, personal. The noun phrase real time is from early 19c. in logic and philosophy, from 1953 as an adjectival phrase in reference to "the actual time during which an event or process occurs," with the rise of computer processes. Get real, usually an interjection, was U.S. college slang in 1960s, reaching wide popularity c. 1987. As a noun, the real, "that which actually exists," by 1818 (Coleridge). The real thing "the genuine article" is by 1818.

Real applies to that which certainly exists, as opposed to that which is imaginary or feigned : as, real cause for alarm ; a real occurrence ; a real person, and not a ghost or a shadow ; real sorrow. Actual applies to that which is brought to be or to pass, as opposed to that which is possible, probable, conceivable, approximate, estimated, or guessed at. [Century Dictionary]

Generally, by the time you are Real, most of your hair has been loved off, and your eyes drop out and you get loose in the joints and very shabby. But these things don't matter at all, because once you are Real you can't be ugly, except to people who don't understand. [Margery Williams, "The Velveteen Rabbit"]