1835, replaced older anormal and abnormous (1742) under influence of L. abnormis "deviating from a rule," from ab- "off, away from" + norma "rule" (see norm). The older forms were via O.Fr. anormal (13c.), from M.L. anormalos, from Gk. anomalos, from an- "not" + homalos, from
homos "same." The Gk. word was altered in Latin by association with norma.