micro-

type of mineral that can be separated easily into extremely thin, tough laminae, 1706, from a Modern Latin specialized use of Latin mica "crumb, bit, morsel, grain."  This is sometimes said to be from the same source as Attic Greek mikros "small" (see micro-). The word was applied to the mineral probably on the supposition that it was related to Latin micare "to flash, glitter" (see micacious). However a recent theory of the origin of the Latin noun does derive it from the same root as micare, on the notion of "a glittering crystalline particle" (originally a grain of salt), which de Vaan finds "formally more attractive" than the connection to the Greek word. Older native names for it were glimmer and cat-silver. Related: Micaceous "containing mica" (1748).

popular name for a bacterium or other extremely small living being, 1878, from French microbe, "badly coined ... by Sédillot" [Weekley] in 1878 from Latinized form of Greek mikros "small" (see micro-) + bios "life" (from PIE root *gwei- "to live"). Intended to mean literally "a small living being," the use of bios is incorrect, as in modern science generally (see bio-); in Greek the compound would mean "short-lived."