Mr. Lowell, in apologizing for this adverb, admits it to be contrary to good usage. The N.E.D. furnishes examples 1549, 1594, 1681, &c. It is not uncommon in the U.S.
1549. In Norfolk [they] are as illy handled as may be.—Duke of Somerset to Sir T. Hoby, Aug. 24. (N.E.D.)
1785. Wisdom, I know, is social. She seeks her fellows, but Beauty is jealous, and illy bears the presence of a rival.—Tho. Jefferson’s ‘Writings’ (1894), iv. 100.
1788. [They] begged for money, which was granted to them, though they illy deserved it.—Mass. Spy, July 24.
1796. The wise editor of the New York Minerva illy bears to have his ignorance exposed.—The Aurora, Phila., Jan. 4.
1797. Should the reply be, we have used [France] illy, and made a British treaty, &c.—Gazette of the U.S., Phila., May 2.
1800. General Pinckney has manifested a temper illy suited to the exalted station for which he is a candidate.—The Aurora, Phila., Sept. 11.
1800. Under the present circumstance, he thought the gentleman calculated illy.—Id., Dec. 31.
1802. Women who were formed of the finer clay, are but illy qualified for the tumultuous scenes and bustles of life; which would hardly fail to sully their reputation, if not to weaken and destroy their virtue.—The Balance, Hudson, N.Y., Jan. 19, p. 17/2.
1803. The road is in many places hilly and rocky, in others very circuitous, and illy accommodated for the ease or despatch of a traveller.—Mass. Spy, March 23.
1807. [The office of supreme judge of the state of New York is] illy rewarded.—The Balance, Oct. 27, p. 341.
1808. This illy accords with your journey to the westward in May; but can you not separate your excursion to this place from the western journey?—Tho. Jefferson to Dr. Wistar, March 20.
1821. Mr. Sully, I fear, however, will consider the trouble of his journey, and the employment of his fine pencil, as illy bestowed on an ottamy of 78.—Thomas Jefferson to Jared Mansfield, Feb. 13. [“Otamy” occurs in Gay’s ‘Beggars’ Opera.’]
1821. Nothing could more illy correspond with the ideas we had formed of our reception among white hunters, than the conduct we had experienced from these men.—H. R. Schoolcraft, ‘Tour in Missouri,’ p. 34 (Lond.).
1822. The drudgery of a compting-room illy agreed with his ardent imagination…. He concluded A.’s turn of mind was illy calculated for the acquirement of property.—Mass. Spy, Jan. 2: from The New-Hampshire Sentinel.
1824. Qui capit ille facit: which by interpretation signifieth, He doth illy face it, who skulketh behind a cape.—Nantucket Inquirer, Jan. 5.
1835. If your curiosity is to hear the backwoodsman, I will assure you I am illy prepared to address this most enlightened people.—‘Col. Crockett’s Tour,’ p. 19 (Phila.).
1840. Such a motive would comport illy with the habits and dispositions of the people.—Mr. Nathan F. Dixon in the U.S. Senate, May 13: Cong. Globe, p. 391.
1850. Mr. Hammond of Md. said the post office building in Baltimore was so illy constructed as not to protect more than fifty persons from rain or other storms.—House of Repr., Aug. 22: id., p. 1627.
1852. When the spirit of persecution manifests itself in the flippancy of rhetoric for female insult and desecration, it is time that I forbear to hold my peace, lest the thundering anathemas of nations born and unborn should rest upon my head, when the marrow of my bones shall be illy prepared to sustain the threatened blow.—Speech of Brigham Young: The Millennial Star, xiv. 402.
1854. I am very illy prepared for vocal gymnastics today.—Mr. C. C. Clay of Ala., U.S. Senate, July 12: Cong. Globe, p. 1704.
1861. New Hampshire paid nothing, being very sparsely settled, very poor in soil, and very illy able to bear any public burden.—O. J. Victor, ‘The History … of the Southern Rebellion,’ i. 207.
1863. The turbulent and illy-informed of the population, would do for voters and soldiers.—Id., ii. 63.
1863. Anderson, when told that the Confederates had not lost a man, expressed his gratification at the bloodless result—a result owing much to the illy-prepared condition of [fort] Sumter’s armament.—Id., ii. 79.
1889. The conduct of W. A. toward the appellant is, to say the least, unkind and ungenerous. Such faithlessness illy accords with the sentiments of honor, justice, and charity, as entertained by the broad-breasted man of sin, however it may be regarded by pious moralists and religious zealots.—Opinion of W. W. Thayer, C.J., in Adams v. Adams, 17th Oregon Reports, p. 253.
1904. In mounting I dropped one of my gauntlets, a scarce article at that time, and one which I could illy afford to lose.—J. H. Claiborne, ‘Seventy-Five Years in Old Virginia,’ p. 268.
