in statistics, "involving or having two or more variables," 1928, from multi- "many" + -variate, from Latin variatio "a difference, variation, change," from past-participle stem of variare "to change" (see vary).
before vowels mult-, word-forming element meaning "many, many times, much," from combining form of Latin multus "much, many," from PIE *ml-to-, from root *mel- (2) "strong, great, numerous." It was much-used in forming Latin compounds in classical times and after (such as multianimis "having much courage," multibibus "much-drinking," multicomus "having much hair," multiloquus "talkative"). Many English words that use it (multinational, etc.) are 20c. coinages.
mid-14c. (transitive); late 14c. (intransitive), from Old French variier "be changed, go astray; change, alter, transform" and directly from Latin variare "change, alter, make different," from varius "varied, different, spotted;" perhaps related to varus "bent, crooked, knock-kneed," and varix "varicose vein," and, more distantly, to Old English wearte "wart," Swedish varbulde "pus swelling," Latin verruca "wart." Related: Varied; varying.
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<a href="https://www.etymonline.com/word/multivariate">Etymology of multivariate by etymonline</a>
Harper, D. (n.d.). Etymology of multivariate. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/multivariate