[dredmorbius]

Both enormous and enormity come from the same etymological roots, enormis "irregular, huge", carrying a connotation of abnormal or irregular, in a negative or bad sense. Enormity specifically came to mean "extreme wickedness" in English, though that meaning is increasingly obscured by usage to mean simply "very big".

Most discerning usage would be that both me "very large scale", but that enormity preserves the meaning of bad at a very large scale.

That's become something of a losing battle as the synonymous usage has become an enormity.

https://www.etymonline.com/word/enormous

https://grammarist.com/usage/enormity-enormousness/