1690s, originally an art criticism term, "assemblage of figures or objects forming a harmonious whole in a painting or design," from French groupe "cluster, group" (17c.), from Italian gruppo "group, knot," which probably is, with Spanish grupo, from a Germanic source, from Proto-Germanic *kruppaz "round mass, lump," part of the general group of Germanic kr- words with the sense "rounded mass" (such as crop (n.).

Extended to "any assemblage, a number of individuals related in some way" by 1736. Meaning "pop music combo" is from 1958. As it was borrowed after the Great Vowel Shift in English, the pronunciation of the -ou- follows French rather than English models.

"form into a group or groups," 1718 (transitive), 1801 (intransitive), from group (n.). Related: Grouped; grouping.

"a number of people of roughly similar age," 1876, originally a term in the science of demographics, from age (n.) + group (n.).

1959, from group (n.) + think.

"act, process, or result of arranging in a group," 1748, verbal noun from group (v.).

also sub-group, 1825, from sub- + group (n.).

"girl who follows pop groups," 1967, from group (n.) in the pop music sense + -ie. In World War II R.A.F. slang it was short for group captain.

also re-group, "to group again, form anew into a group," 1838, from re- "again" + group (v.). Related: Regrouped; regrouping; regroupment.

"internet discussion group within the Usenet system containing messages posted from users in different locations," by 1985, from news (n.), perhaps on the notion of sharing news of a particular topic, + group (n.).

1610s, "action of arranging into kinds or classes," from assort + -ment. The sense of "group of things of the same sort" is attested from 1759; that of "group of arranged things whether of the same sort or not" from 1791.