norm n.

"not conformed or conforming to rule, deviating from a type or standard, contrary to system or law, irregular, unnatural," 1835, a refashioning of anormal (q.v.) under influence of Latin abnormalis "deviating from a fixed rule, irregular," from ab "off, away from" (see ab-) + norma "rule" (see norm).

The older form was from French anormal (13c.), from Medieval Latin anormalus, an altered (by association with norma) borrowing of Greek anomalos "uneven, irregular," from an- "not" (see an- (1)) + homalos "even," from homos "same" (from PIE root *sem- (1) "one; as one, together with"). Compare anomaly. "Few words show such a series of pseudo-etymological perversions" [Weekley]. Another adjective was abnormous (1742) "irregular, misshapen," from Latin abnormis. Related: Abnormally.

1530s, "abnormal" (usually in a bad sense), from Latin enormis "out of rule, irregular, shapeless; extraordinary, very large," from assimilated form of ex "out of" (see ex-) + norma "rule, norm" (see norm), with English -ous substituted for Latin -is. Meaning "extraordinary in size" is attested from 1540s; original sense of "outrageous" is more clearly preserved in enormity. Earlier was enormyous (mid-15c.) "exceedingly great, monstrous." Related: Enormously; enormousness.