Origin and history of underclass

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)." This is reconstructed to be from PIE root *kele- (2) "to shout" (Watkins). In early use in English also in Latin form classis.

The 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. The natural history sense "group of related plants or animals" is from 1753.

The meaning "high quality" is from 1874. The sense of "a division of society according to status" (with upper, lower, etc.) is attested by 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]

Old English under (prep.) "beneath, among, before, in the presence of, in subjection to, under the rule of, by means of," also, as an adverb, "beneath, below, underneath," expressing position with reference to that which is above.

It is reconstructed to be from Proto-Germanic *under- (source also of Old Frisian under, Dutch onder, Old High German untar, German unter, Old Norse undir, Gothic undar), from PIE *ndher- "under" (source also of Sanskrit adhah "below;" Avestan athara- "lower;" Latin infernus "lower," infra "below").

It was productive as a prefix in Old English, as in German and Scandinavian (often forming words modeled on Latin ones in sub-); Middle English had more than 200 words with it.

The notion of "inferior in rank, position, etc." was present in Old English. With reference to standards, "less than in age, price, value," etc., late 14c. As an adjective, "lower in position; lower in rank or degree" from 13c. Also used in Old English as a preposition meaning "between, among," as still in under these circumstances, etc. (though this may be a different root; compare understand).

In many figurative expressions: To keep something under (one's) hat "secret" is from 1885; to have something under (one's) nose "in plain sight" is from 1540s; to get something under (one's) belt was literally to eat or drink it (1839), figurative use is by 1931. To be under (someone's) wing "protected by (someone)" is recorded from early 13c.

To speak under (one's) breath "in a low voice" is attested by 1832.