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.
"act or fact of sharing or partaking in common with another or others; act or state of receiving or having a part of something," late 14c., participacioun, from Old French participacion (13c.) and directly from Late Latin participationem (nominative participatio) "partaking," noun of action from past-participle stem of Latin participare "participate in, share in, partake of; to make partaker, to share, impart," from particeps (genitive participis) "partaker, comrade, fellow soldier," also, as an adjective, "sharing, partaking," from pars (genitive partis) "a part, piece, a division" (from PIE root *pere- (2) "to grant, allot") + -cip-, weak form of stem of capere "to take," from PIE root *kap- "to grasp." Related: Participational "involving or requiring participation" (1952).
late 14c., communioun, "participation in something; that which is common to all; union in religious worship, doctrine, or discipline," from Old French comunion "community, communion" (12c.), from Latin communionem (nominative communio) "fellowship, mutual participation, a sharing," used in Late Latin ecclesiastical language for "participation in the sacrament," from communis "common, general" (see common (adj.)).
Used by Augustine, in belief that the word was derived from com- "with, together" + unus "oneness, union." In English, from mid-15c. as "the sacrament of the Eucharist," from c. 1500 as "act of partaking in the sacrament of the Eucharist." From 1610s as "intercourse between two or more."
"one who participates, a partaker," 1560s, from French participant, from Latin participantem (nominative participans), present participle of participare "to share in, partake of" from particeps "sharing, partaking" (see participation).
1580s, from French initiation or directly from Latin initiationem (nominative initiatio) "participation in secret rites," noun of action from past-participle stem of initiare "originate, initiate," from initium "a beginning" (see initial (adj.)).
"sharing, having a share or part," late 15c., from Old French participant and directly from Latin participantem (nominative participans), present participle of participare "to share in, partake of," from particeps "sharing, partaking" (see participation).