early 15c., from un- (1) "not" + past participle of divide (v.).
Entries linking to undivided
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.
divide v.
early 14c., "separate into parts or pieces," from Latin dividere "to force apart, cleave, distribute," from assimilated form of dis- "apart" (see dis-) + -videre "to separate," which, according to de Vaan, is from PIE *(d)uid- "to separate, distinguish" (source also of Sanskrit avidhat "allotted," Old Avestan vida- "to devote oneself to"). He writes: "The original PIE verb ... (which became thematic in Latin) meant 'to divide in two, separate'. It lost initial *d- through dissimilation in front of the next dental stop, and was reinforced by dis- in Latin ...." Also compare devise.
It is attested from late 14c. as "sever the union or connection with," also "disunite, cause to disagree in opinion." Intransitive sense of "become separated into parts" is from 1520s. Mathematical sense "perform the operation of division" is from early 15c. Divide and rule (c. 1600) translates Latin divide et impera, a maxim of Machiavelli. Related: Divided; dividing.