Laudator Temporis Acti

George H.W. Bush, Speech to the Parliament of Poland (July 10, 1989):

The reform of the Polish economy presents an historic challenge. There can be no substitute for Poland's own efforts, but I want to stress to you today that Poland is not alone. Given the enormity of this moment, the United States stands ready to help, as you help yourselves.

Barack Obama, Speech at rally in Grant Park in Chicago (Nov. 5, 2008):

This is your victory. And I know you didn't do this just to win an election. And I know you didn't do it for me. You did it because you understand the enormity of the task that lies ahead.

Judith Warner, Tears to Remember (New York Times, Nov. 6, 2008):

But the race thing? The groundbreaking enormity of the election of our country's first African-American president?

I'm a fuddy-duddy, and I cringe when I hear or read enormity with the meaning "hugeness, importance." My catechism, Strunk and White's Elements of Style, prescribes: "Use only in the sense of 'monstrous wickedness.'" But some authorities give the other meaning their stamp of approval, e.g. Merriam-Webster's Concise Dictionary of English Usage: "The stigmatized sense is entirely standard and has been for over a century and a half."

The word comes from Latin, and the "big" meaning is common in that language, according to Lewis & Short. First the adjective:

ē-normis, e, adj. [norma],

I. out of rule (post-Aug.).

I. Irregular, unusual: toga, Quint. 11, 3, 139 : vici (with huc et illuc flexi), Tac. A. 15, 38 .--Far more freq.,

II. Immoderate, immense, enormous (cf.: immensus, immodicus, summus, maximus, effusus): enormes sunt (umbrae) cerasis, Plin. 17, 12, 17, § 88: spatium (with immensum), Tac. Agr. 10; cf. hastae (with immensa scuta), id. A. 2, 14 : gladii (opp. parva scuta), id. Agr. 36: Colossi, Stat. S. 1, 3, 51; cf. corpus, Suet. Calig. 50 : proceritas, id. Vitell. 17: uniones, Plin. 9, 35, 56, § 115 et saep.: senecta, i.e. very great, App. 9, p. 232; Sen. ap. Gell. 12, 2, 10: loquacitas, Petr. 2, 7; cf. Plin. Ep. 9, 26, 6.-- Comp.: prologus enormior quam fabula, longer, Spart. Ael. Ver. 1 fin.--Adv.: ēnor-mĭter (acc. to I.), irregularly, Sen. Q. N. 1, 7; Plin. 36, 10, 15, § 17; 37, 6, 23, § 89; Veg. Vet. 2, 8, 2; 2, 28, 10; 1, 36; 56 Bip.-- Sup. of the adj. and comp. and sup. of the adv. appear not to occur.

Next the noun:

ēnormĭtas , ātis, f. [enormis] (postAug.).

I. Irregularity, Quint. 9, 4, 27.--

II. Hugeness, vastness, enormous size, Sen. Const. Sap. 18: onerum, Veg. Vet. 2, 54; 59 Bip.; Spart. Carac. 2; Capitol. Gord. 29 al.