c. 1400, "devoted to or relating to home life;" 1560s as "living with others," from French social (14c.) and directly from Latin socialis "of companionship, of allies; united, living with others; of marriage, conjugal," from socius "companion, ally," probably originally "follower," from PIE *sokw-yo-, suffixed form of root *sekw- (1) "to follow." Compare Old English secg, Old Norse seggr "companion," which seem to have been formed on the same notion). Related: Socially.
Sense of "characterized by friendliness or geniality" is from 1660s. Meaning "living or liking to live with others; companionable, disposed to friendly intercourse" is from 1720s. Meaning "of or pertaining to society as a natural condition of human life" first attested 1695, in Locke. Sense of "pertaining to fashionable society" is from 1873.
Social climber is from 1893; social work is 1890; social worker 1886. Social drinking first attested 1807. Social studies as an inclusive term for history, geography, economics, etc., is attested from 1916. Social security "system of state support for needy citizens" is attested from 1907 (the Social Security Act was passed by U.S. Congress in 1935). Social butterfly is from 1867, in figurative reference to "flitting."
Social contract (1763) is from translations of Rousseau. Social Darwinism attested from 1887. Social engineering attested from 1899. Social science is from 1785. In late 19c. newspapers, social evil is "prostitution." Social network is attested by 1971; social networking by 1984; social media by 2008. Social justice is attested by 1718.
I must introduce a parenthetical protest against the abuse of the current term 'social justice'. From meaning 'justice in relations between groups or classes' it may slip into meaning a particular assumption as to what these relations should be; and a course of action might be supported because it represented the aim of 'social justice', which from the point of view of 'justice' was not just. The term 'social justice' is in danger of losing its rational content—which would be replaced by a powerful emotional charge. I believe that I have used the term myself: it should never be employed unless the user is prepared to define clearly what social justice means to him, and why he thinks it just. [T.S. Eliot, footnote in "Notes Towards the Definition of Culture," 1948]
1705, "to divide into classes, place in ranks or divisions," from class (n.) or French classer. Sense of "to place into a class" is from 1776. Related: Classed; classing.
c. 1600, "group of students," in U.S. especially "number of pupils in a school or college of the same grade," from French classe (14c.), from Latin classis "a class, a division; army, fleet," especially "any one of the six orders into which Servius Tullius divided the Roman people for the purpose of taxation;" traditionally originally "the people of Rome under arms" (a sense attested in English from 1650s), and thus akin to calare "to call (to arms)," from PIE root *kele- (2) "to shout." In early use in English also in Latin form classis.
Meaning "an order or rank of persons, a number of persons having certain characteristics in common" is from 1660s. School and university sense of "course, lecture" (1650s) is from the notion of a form or lecture reserved to scholars who had attained a certain level. Natural history sense "group of related plants or animals" is from 1753. Meaning "high quality" is from 1874. Meaning "a division of society according to status" (with upper, lower, etc.) is from 1763. Class-consciousness (1903) is from German Klassenbewusst.
The fault, the evil, in a class society is when privilege exists without responsibility and duty. The evil of the classless society is that it tends to equalize the responsibility, to atomize it into responsibility of the whole population—and therefore everyone becomes equally irresponsible. [T.S. Eliot, BBC interview with Leslie Paul, 1958]
"belonging to the class next after the first," 1833, from the noun phrase (1810) indicating the second of a ranked series of classes (originally in a university, later of railroad accommodations, etc.), from second (adj.) + class (n.). The phrase second-class citizen is recorded from 1942 in U.S. history.
The Negro recognizes that he is a second-class citizen and that status is fraught with violent potentialities, particularly today when he is living up to the full responsibilities of citizenship on the field of battle. [Louis E. Martin, "To Be or Not to Be a Liberal," in The Crisis, September 1942]
1766, in a British sense, "class of people socially intermediate between the aristocratic and the laboring classes, the community of untitled but well-bred or wealthy people," from middle (adj.) + class (n.). As an adjective, "pertaining to the middle class," by 1857, with reference to education. Nares reports menalty as an early word for "the middle class" (1540s).