"a right, a legal claim to one's due," mid-15c., from Old French droit, dreit "right," from Medieval Latin directum (contracted drictum) "right, justice, law," neuter or accusative of Latin directus "straight," past participle of dirigere "set straight" (see direct (v.)).
Droit du seigneur (1825)), from French (1784), was the alleged medieval custom giving a feudal lord the right to have sex with the bride of his vassal on their wedding night before she went to her husband; literally "the lord's right." There is little evidence that it actually existed; it seems to have been invented in imagination 16c. or 17c. The Latin form was jus primae noctis, "law of the first night." For French droit, see right (adj.2).
also colour-blindness, "incapacity for perceiving certain colors due to an absence or weakness of the sensation upon which the power of distinguishing them depends," 1844, the native word, used in England instead of French daltonisme (by 1828), after English chemist John Dalton (1766-1844), who published a description of it in 1794. From color (n.) + blindness.
The continental philosophers have named it Daltonism, a name which has been strongly objected to by almost every English writer who has discussed the subject, on the ground of the inexpediency and undesirableness of immortalizing the imperfections or personal peculiarities of celebrated men by title of this kind. ... The name "Color-Blindness," proposed by Sir D. Brewster, seems in every respect unexceptionable. [Littell's Living Age, vol. v, April 1845]
Noted as inexact (very few people who can see are blind to all color), "the term is applied with much laxity to any constitutional inability to discriminate between colours" [OED]. In figurative use, with reference to race or ethnicity, it is attested from 1866, American English. Related: color-blind (adj.), which is attested from 1854.