unyielding (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.

Old English gieldan (West Saxon), geldan (Anglian) "to pay, pay for; reward, render; worship, serve, sacrifice to" (class III strong verb; past tense geald, past participle golden), from Proto-Germanic *geldan "pay" (source also of Old Saxon geldan "to be worth," Old Norse gjaldo "to repay, return," Middle Dutch ghelden, Dutch gelden "to cost, be worth, concern," Old High German geltan, German gelten "to be worth," Gothic fra-gildan "to repay, requite"). This is from PIE *gheldh- "to pay," a root found only in Balto-Slavic and Germanic (and Old Church Slavonic žledo, Lithuanian geliuoti might be Germanic loan-words).

"[T]he only generally surviving senses on the Continent are 'to be worth; to be valid, to concern, apply to,' which are not represented at all in the English word" [OED]; sense development in English comes via use of this word to translate Latin reddere, French rendre. Sense of "give in return for labor or capital invested" is from early 14c. Intransitive sense of "give oneself up, submit, surrender (to a foe)" is from c. 1300. Related to Middle Low German and Middle Dutch gelt, Dutch geld, German Geld "money." Related: Yielded; yielding.