"capable of combining partly with one element, partly with another," 1881, from poly- + -valent (see valence in the chemistry sense). Coined by German chemist Emil Erlenmeyer, who also designed the flask that bears his name.
word-forming element meaning "many, much, multi-, one or more," from Greek polys "much" (plural polloi), from PIE root *pele- (1) "to fill," with derivatives referring to multitudinousness or abundance. Equivalent to Latin multi-, it is properly used in compounds only with words of Greek origin. In chemical names, usually indicating a compound with a large number of atoms or molecules of the same kind (such as polymer).
early 15c., "extract, preparation," from Latin valentia "strength, capacity," from valentem (nominative valens) "strong, stout, vigorous, powerful," present participle of valere "be strong" (from PIE root *wal- "to be strong"). Chemistry sense of "relative combining capacity of an element with other atoms when forming compounds or molecules" is recorded from 1884, from German Valenz (1868), from the Latin word. Related: Valency.
It is the hypothetical source of/evidence for its existence is provided by: Latin valere "be strong, be well, be worth;" Old Church Slavonic vlasti "to rule over;" Lithuanian valdyti "to have power;" Celtic *walos- "ruler," Old Irish flaith "dominion," Welsh gallu "to be able;" Old English wealdan "to rule," Old High German -walt, -wald "power" (in personal names), Old Norse valdr "ruler."
<a href="https://www.etymonline.com/word/polyvalent">Etymology of polyvalent by etymonline</a>
Harper, D. (n.d.). Etymology of polyvalent. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/polyvalent