Origin and history of unreal

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"]

1804 (Southey), "make unreal;" see unreal + -ize. Unrealizable "incapable of being realized" is by 1840 (Carlyle).

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."

The most prolific of English prefixes, freely and widely used in Old English, where it forms more than 1,000 compounds. 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.

Often euphemistic (untruth for "a lie") or emphatic, if there is a sense already of divestment or releasing: unpeel " to peel;" unpick "pick (a lock) with burglars' tools;" unloose for "to loosen."

It also makes words from phrases, such as uncalled-for, c. 1600; undreamed-of, 1630s. Fuller (1661) has unbooklearned. A mid-15c. description of a legal will has unawaydoable; Ben Jonson has un-in-one-breath-utterable. The word uncome-at-able is attested by 1690s in Congreve, frowned at by Samuel Johnson in the 18th century and by Fowler in the 20th ("The word had doubtless, two or three centuries ago, a jolly daredevil hang-the-grammarians air about it ; that has long evaporated ; it serves no purpose that inaccessible does not ....").

But the practice continued; unlawlearned (Bentham, 1810), unlayholdable (1860); unputdownable, of a book, is by 1947; unpindownable, by 1966. Also compare put-up-able-with (1812). As a prefix in telegraphese, to replace not and save the cost of a word, it is attested by 1936.

With the variety of its possible use, and the need for negatives, the number of un- words that might be made in English is almost endless, and that some are used and some never is owing to the caprice of authors.

Dictionary editors noted this since 18c. but also padded the list. John Ash's "New and Complete Dictionary of the English Language" (1775) has many pages of one-line un- entries; among a dozen consecutive entries are unhaggled, unhaired, unhalooed, unhaltering (adj.), unhaltering (n.), which sorts of words OED (1989) notes were "obviously manufactured for the purpose" and some turn up in other texts only decades later, if at all. (Ash vindicated.)