also microorganism, "a microscopic organism," 1855, from micro- + organism.
Entries linking to micro-organism
micro-
word-forming element meaning "small in size or extent, microscopic; magnifying;" in science indicating a unit one millionth of the unit it is prefixed to; from Latinized form of mikros, Attic form of Greek smikros "small, little, petty, trivial, slight," perhaps from PIE *smika, from root *smik- "small" (source also of Old High German smahi "littleness"), but Beekes thinks it a Pre-Greek word.
organism n.
1660s, "organic structure, organization" (a sense now rare or obsolete), from organize + -ism. Sense of "living animal or plant, body exhibiting organic life" is by 1842. Related: Organismic; organismal.