It is common these days to hear about the enormity of terrible events. Some people flinch at the misuse; others take it in their stride; most don’t recognise the problem.
It is easy to see why many people understand enormity as the quality of being enormous. Strictly, the current meaning of enormous is ‘very large, huge’; and the true current meaning of enormity is ‘extreme or monstrous wickedness’.
The problem is that we do not have many convenient words for the condition of being very large: enormousness is clumsy, hugeness is unconvincing, largeness is not big enough, vastness suggests expanse rather than size, magnitude suggests Olympian indifference. Another possible contender is immane: ‘monstrous in size or strength; huge, vast, enormous, tremendous’, from the Latin immanis ‘monstrous, huge, savage, (from im- + manus ‘hand’). Not a common word, and not likely to be understood immediately by anyone without a large dictionary readily to hand. The most recent use of it recorded by OED2 is from 1860: Oliver Wendell Holmes (the poetic father, not the judicial son) wrote of ‘that immane and nefandous Burke-and-Hare business’. Anyone who uses nefandous so casually must have high expectations of their audience. (Nefandous: unmentionable; abominable, atrocious.) Interestingly, you see in this example that immane combines notions of size and wickedness which were also present early in enormous / enormity.
So, while enormity fits the bill and seems well adapted to the task of describing the condition of being very big, purists resist it. To them, enormity immediately suggests vileness, baseness, wickedness. They are right, of course — although being right is never decisive in matters of language. Enormity and enormous have the same origin and originally had related meanings. They denote departure from the norm, generally in a way that attracted opprobrium. The earliest (but now obsolete) meaning of enormous is given as:
Deviating from ordinary rule or type; abnormal, unusual, extraordinary, unfettered by rules; hence, mostly in bad sense, strikingly irregular, monstrous, shocking; excessively wicked, flagitious, outrageous.
In King Lear, Kent hopes that Cordelia
… shall find time
From this enormous state, seeking to give
Losses their remedies.
(King Lear, Act II: ii)
Edmund Burke wrote in 1790, in his Reflections on the Revolution in France, that: ‘They see with horror and alarm that enormous and shameless act of proscription.’ And Boswell, in his Life of Samuel Johnson (1791) wrote of ‘the detection of some enormous crime’. But by the early nineteenth century the original sense had been displaced. In 1847, Emily Brontë wrote in Wuthering Heights of ‘a pair of enormous slippers’ with no suggestion that the slippers inspired fear or called for censure.
By contrast, enormity retained its original sense of wickedness. In The Voyage of the Beagle, Darwin sets out in an entry from his diary for 5 September 1834 that some of the locals, having been converted to Christianity on the Catholic side, could not understand the habits of the episcopalian church: ‘The absurdity of a bishop having a wife particularly struck them: they scarcely knew whether to be most amused or horror-struck at such an enormity.’
James Joyce wrote in A Portrait of the Artist as a Young Man (1916):
Sin, remember, is a twofold enormity. It is a base consent to the promptings of our corrupt nature to the lower instincts, to that which is gross and beastlike; and it is also a turning away from the counsel of our higher nature …
The OED2 recognises ‘largeness’ as an obsolete meaning of enormity, but comments archly that ‘recent examples might perhaps be found, but the use is now regarded as incorrect’.
The OED2 definition of enormous introduces another word for the (original) idea: flagitious. This is a real rarity and it is odd to find it in a definition, since dictionary definitions generally aim to describe the headword in terms more simple than the word being defined. (A famous departure from this principle is Johnson’s definition of network: ‘Any thing reticulated or decussated, at equal distances, with interstices between the intersections.’)
Flagitious means ‘guilty of or addicted to atrocious crimes; deeply criminal, extremely wicked’.
In 1591, Christopher Marlowe wrote:
Tears falling from repentant heaviness
Of thy most vile and loathsome filthiness,
The stench whereof corrupts the inward soul
With such flagitious crimes of heinous sins
As no commiseration may expel …
(Doctor Faustus)
And in 1692 John Locke wrote in his ‘Letter Concerning Toleration’:
Ecclesiastical assemblies and sermons are justified by daily experience and public allowance … These meetings ought not to be sanctuaries for factious and flagitious fellows.
The latest use of the word noted by OED2 dates from 1879, and, perhaps appropriately, is a statement by that pillar of conspicuous virtue Sir William Gladstone who spoke of ‘the most flagitious of mortals’.