1520s; see un- (1) "not" + righteous (adj.). In Middle English, the word was unrightwis, from Old English unrihtwis. Related: Unrighteously; unrighteousness.
Entries linking to unrighteous
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.
righteous adj.
an early 16c. alteration of the older word, rightwise, which is from Old English rihtwis, of actions, "characterized by justice, morally right," of persons, "just, upright; sinless, conforming to divine law," from riht (see right (adj.1)) + wis "wise, way, manner" (see wise (adj.)). The alteration of the ending is by influence of courteous, etc. As a noun, "those who are righteous," Old English rehtwisan. The meaning "genuine, excellent" is 1942 in jazz slang. Related: Righteously.
Upright gets force from the idea of physical perpendicularity, a standing up straight by the standard of right ; righteous carries up the idea of right to the standards, motives, and sanctions of religion ; rightful applies not to conduct, but to claims by right : as, he is the rightful owner of the land ; just suggests by derivation a written law, but presumes that the law is a right one, or that there is above it, and if necessary overruling it, a law of God. This last is the uniform Biblical usage. Just generally implies the exercise of some power or authority. [Century Dictionary]