1560s, "not argued with," from un- (1) "not" + past participle of dispute (v.). Meaning "not called into question" is attested from 1620s.
Entries linking to undisputed
un- 1
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.
dispute v.
c. 1300, "engage in argumentation or discussion," from Old French desputer (12c.) "dispute, fight over, contend for, discuss" and directly from Latin disputare "weigh, examine, discuss, argue, explain," from dis- "separately, apart" (see dis-) + putare "to count, consider," originally "to prune, make clean, clear up" (from PIE root *pau- (2) "to cut, strike, stamp").
The Latin word was used in Vulgate in sense of "to argue, contend with words." In English, transitive sense of "argue against, attempt to disprove, deny" is from 1510s. Related: Disputable; disputed; disputing.