unchanging (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.

c. 1200, "to alter, make different, change" (transitive); early 13c. as "to substitute one for another;" mid-13c. as "to make (something) other than what it was, cause to turn or pass from one state to another;" from late 13c. as "to become different, be altered" (intransitive), from Old French changier "to change, alter; exchange, switch," from Late Latin cambiare "to barter, exchange," extended form of Latin cambire "to exchange, barter." This is held to be of Celtic origin, from PIE root *kemb- "to bend, crook" (with a sense evolution perhaps from "to turn" to "to change," to "to barter"); cognate with Old Irish camm "crooked, curved;" Middle Irish cimb "tribute," cimbid "prisoner;" see cant (n.2).

From c. 1300 as "undergo alteration, become different." In part an abbreviation of exchange. From late 14c. especially as "to give an equivalent for in smaller parts of the same kind" (money). The meaning "to take off clothes and put on other ones" is from late 15c. Related: Changed;changing. To change (one's) mind is from 1590s.