Enormous means far bigger than you expected. An enormous dog that fills the whole back seat, an enormous slice of cake you cannot finish, an enormous suitcase for a two-day trip.
It stretches past size into amount and feeling: enormous pressure, an enormous amount of work, enormous relief when the results came through. It is already stronger than big, strong enough that very in front of it adds nothing — say enormous, not very enormous. The adverb is enormously, and it works on verbs and adjectives alike: it helped enormously, she was enormously pleased. Enormity is the trap waiting for you. It does not mean enormousness; it means the shocking wickedness of an act, as in the enormity of the crime.
1adjectiveenormousExtremely large in size.
“An enormous oak stands at the end of the garden.”
2adjectivegreatExtremely great in amount or degree.
“She put an enormous amount of work into the report.”
Too few real examples of this word to estimate which sense is commonest.
Enormous came from Latin ēnormis, built out of ex- (out of) and norma (a rule or norm). Something enormous is outside the norm — off the scale rather than merely large. English kept the size and let go of the wrongness, which survives instead in enormity.
Latin
ēnormis
English, today
enormous
Built from
From Latin ēnormis. An assimilated form of ex- + norma (“rule, norm”) + -ous.
Etymology from Wiktionary, CC BY-SA