quadru-

before vowels quad- (before -p- often quadru-, from an older form in Latin), word-forming element used in compounds of Latin origin and meaning "four, four times, having four, consisting of four," from Latin quadri-, which is related to quattor "four" (from PIE root *kwetwer- "four").

1875, in reference to telegraph systems in which four messages can be wired simultaneously, from quadru- + -plex. In classical Latin, quadruplex meant "fourfold, quadruple," as a noun, "a fourfold amount." Related: Quadruplicity "fourfold nature," 1580s, from Latin quadruplicitas, noun of quality from quadruplex.