Sherron Westerfield made this judicious remark in her column Points to Ponder, published in The Advocate-Messenger (Danville, Kentucky) of 27^th November 2001:

“Don’t confuse me with the facts. My mind is made up.” This rallying cry of the ultracrepidarians, or those who proffer their opinions on matters about which they are ill-informed, frequently leaps out at me from editorials, reviews, and national news.

As an adjective, ultracrepidarian means expressing opinions on matters outside the scope of one’s knowledge or expertise; as a noun, it denotes a person who expresses such opinions.

This word was specifically invented to qualify the English poet and critic William Gifford (1756-1826), born in Ashburton, Devon (a detail mentioned by Leigh Hunt in his poem—see below). The son of a glazier, Gifford served an apprenticeship to a shoemaker before, supported by William Cookesley, a local surgeon, attending Exeter College, Oxford; he was, from 1809 to 1824, the first editor of The Quarterly Review.

With reference to the fact that William Gifford had been a shoemaker’s apprentice, ultracrepidarian alludes to the remark “ne supra crepidam sutor iudicaret”, “the cobbler should not judge beyond his shoe”, attributed to the painter Apelles in response to criticism from a shoemaker, in Naturalis Historia (The Natural History – 77), a vast encyclopaedia of the natural and human worlds by the Roman statesman and scholar Pliny the Elder (23-79). This anecdote is the origin of the proverb let the cobbler stick to his last. (The word ultracrepidarian is from Latin ultra, meaning beyond, and crĕpĭda (from Greek κρηπίς [= krēpís]), denoting the sole which served the Greeks, and the Romans who adopted Grecian habits, as a shoe, a sandal.)

The word ultracrepidarian was first used as an adjective qualifying the noun critic by the English writer and painter William Hazlitt (1778-1830) in A Letter to William Gifford, Esq. (London, 1819):

(from The collected works of William Hazlitt – London, 1902)
Your overweening self-complacency is never easy but in the expression of your contempt for others; like a conceited mechanic in a village ale-house, you would set down every one who differs from you as an ignorant blockhead; and very fairly infer that any one who is beneath yourself must be nothing. You have been well called an Ultra-Crepidarian critic.

In 1823, James Henry Leigh Hunt (1784-1859), English poet, journalist and critic, published Ultra-Crepidarius, a satirical poem on William Gifford: Mercury, rising one morning, misses one of his winged shoes; Venus, with whom he is living, confesses that she has “sent down to earth this same Shoe with an errand To get a new pair at Ashburton for her”. The shoe is not returning, so the god and goddess agree to go in search of it, and scarcely alight before they stumble on a shoe, which behaves with the greatest disrespect to everything light, airy, beautiful or winged, until, exasperated, Mercury transforms it into William Gifford:

(from Spenser and the Tradition: English poetry 1579-1830)
The poor Shoe, turning restless and wan,
Gave a groan, and began struggling up into man.
First the straps, falling stiffly, and thrusting the ground,
Became arms, by whose help it arose, turning round;
Then the toe split in two, and increasing in size,
Undertook to support him as legs and as thighs;
And lastly from out of the quartering there looked
A face at once lachrymose rude, and rebuked.
Such a face! Such a spirit! For what is a face,
But what the soul makes it, for worth or disgrace?

Like a rogue from a regiment be-drummered and fifered,
It slunk out of doors, and men called the thing GIFFORD.