Enormous

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mid 16th century: from Latin enormis ‘unusual, huge’ (see enormity) + -ous.

wiktionary

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From Latin ēnormis. An assimilated form of ex-(“out of”) + norma(“rule, norm”) + -ous.

etymonline

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enormous (adj.)

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.