"morally correct," Old English riht "just, good, fair; proper, fitting; straight, not bent, direct, erect," from Proto-Germanic *rehtan (source also of Old Frisian riucht "right," Old Saxon reht, Middle Dutch and Dutch recht, Old High German reht, German recht, Old Norse rettr, Gothic raihts), from PIE root *reg- "move in a straight line," also "to rule, to lead straight, to put right" (source also of Greek orektos "stretched out, upright;" Latin rectus "straight, right;" Old Persian rasta- "straight; right," aršta- "rectitude;" Old Irish recht "law;" Welsh rhaith, Breton reiz "just, righteous, wise").
Compare slang straight (adj.1) "honest, morally upright," and Latin rectus "right," literally "straight," Lithuanian teisus "right, true," literally "straight." Greek dikaios "just" (in the moral and legal sense) is from dike "custom." As an emphatic, meaning "you are right," it is recorded from 1580s; use as a question meaning "am I not right?" is from 1961.
The sense in right whale (by 1733) is said in dictionaries to be "justly entitled to the name;" earliest sources for the term, in New England whaling publications, list it first among whales and compare the others to it. Right stuff "best human ingredients" is from 1848, popularized by Tom Wolfe's 1979 book about the first astronauts. Right of way is attested from 1767. Right angle is from late 14c.
"opposite of left," early 12c., riht, from Old English riht, which did not have this sense but meant "good, proper, fitting, straight" (see right (adj.1)). The notion is of the right hand as the "correct" hand. The usual Old English word for this was swiþra, literally "stronger." "The history of words for 'right' and 'left' shows that they were used primarily with reference to the hands" [Buck]. Similar sense evolution in Dutch recht, German recht "right (not left)," from Old High German reht, which meant only "straight, just." Compare Latin rectus "straight; right," also from the same PIE root.
The usual PIE root (*dek-) is represented by Latin dexter (see dexterity). Other derivations on a similar pattern to English right are French droit, from Latin directus "straight;" Lithuanian labas, literally "good;" and Slavic words (Bohemian pravy, Polish prawy, Russian pravyj) from Old Church Slavonic pravu, literally "straight," from PIE *pro-, from root *per- (1) "forward," hence "in front of, before, first, chief."
The political sense of "conservative" is first recorded 1794 (adj.), 1825 (n.), a translation of French Droit "the Right, Conservative Party" in the French National Assembly (1789; see left (adj.)).
Old English rihtan "to straighten, rule, set up, set right, amend; guide, govern; restore, replace," from riht (adj.); see right (adj.1). Compare Old Norse retta "to straighten," Old Saxon rihtian, Old Frisian riuchta, German richten, Gothic garaihtjan. Related: Righted; righting.
Old English riht (West Saxon, Kentish), reht (Anglian), "that which is morally right, duty, obligation," also "rule of conduct; law of a land;" also "what someone deserves; a just claim, what is due; correctness, truth; a legal entitlement, a privilege," from the root of right (adj.1). Meaning "the right" (as opposed to the left) is from mid-13c.; political use from 1825. From early 14c. as "a right action, a good deed." Meaning "a blow with the right fist" is from 1898. The phrase to rights "at once, straightway" is 1660s, from sense "in a proper manner" (Middle English).
Old English rehte, rihte "in a straight or direct manner," from right (adj.1). Right on! as an exclamation of approval first recorded 1925 in African-American vernacular, popularized mid-1960s by Black Panther movement.