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.
It is the hypothetical source of/evidence for its existence is provided by: Latin loqui "to speak;" Old Irish ad-tluch- "to thank," to-tluch- "to ask;" Old Church Slavonic tloko "interpretation, explanation."
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<a href="https://www.etymonline.com/word/multiloquent">Etymology of multiloquent by etymonline</a>
Harper, D. (n.d.). Etymology of multiloquent. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/multiloquent