"made shut, not open," c. 1200, past-participle adjective from close (v.). Closed circuit "complete, unbroken (electrical) circuit" is attested from 1827; closed shop"workplace in which only union members are employed" is from 1904; closed system first recorded 1896 in William James as "complete and unalterable system (of doctrines, etc.)." Later used in a physical sense, "system in which the total mass or energy remains constant."
Old English word "speech, talk, utterance, sentence, statement, news, report, word," from Proto-Germanic *wurda- (source also of Old Saxon, Old Frisian word, Dutch woord, Old High German, German wort, Old Norse orð, Gothic waurd), from PIE *were- (3) "speak, say" (see verb).
The meaning "promise" was in Old English, as was the theological sense. In the plural, the meaning "verbal altercation" (as in have words with someone) dates from mid-15c. Word-processor first recorded 1971; word-processing is from 1972; word-wrap is from 1977. A word to the wise is from Latin phrase verbum sapienti satis est "a word to the wise is enough." Word-for-word "in the exact word or terms" is late 14c. Word of mouth "spoken words, oral communication" (as distinguished from written words) is by 1550s.
It is dangerous to leave written that which is badly written. A chance word, upon paper, may destroy the world. Watch carefully and erase, while the power is still yours, I say to myself, for all that is put down, once it escapes, may rot its way into a thousand minds, the corn become a black smut, and all libraries, of necessity, be burned to the ground as a consequence. [William Carlos Williams, "Paterson"]
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]