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., "tool to indicate a horizontal line," from Old French livel "a level" (13c.), ultimately from Latin libella "a balance, level" (also a monetary unit), diminutive of libra "balance, scale, unit of weight" (see Libra). Spanish nivel, Modern French niveau are from the same source but altered by dissimilation.
Meaning "position as marked by a horizontal line" (as in sea-level) is from 1530s; meaning "flat surface" is from 1630s; meaning "level tract of land" is from 1620s. Figurative meaning in reference to social, moral, or intellectual condition is from c. 1600. Figurative phrase on the level "fair, honest" is from 1872; earlier it meant "moderate, without great ambition" (1790).
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Harper, D. (n.d.). Etymology of multilevel. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/multilevel