Wiktionary
n. The habit or act of giving opinions on matters outside the scope of one's knowledge.
Wikipedia
__notoc__ Ultracrepidarianism is the habit of giving opinions and advice on matters outside of one's knowledge.
The term ultracrepidarian was first publicly recorded in 1819 by the essayist William Hazlitt in an open Letter to William Gifford, the editor of the Quarterly Review: "You have been well called an Ultra-Crepidarian critic." It was used again four years later in 1823, in the satire by Hazlitt's friend Leigh Hunt, Ultra-Crepidarius: a Satire on William Gifford.
The term draws from a famous comment purportedly made by Apelles, a famous Greek artist, to a shoemaker who presumed to criticise his painting. The Latin phrase " Sutor, ne ultra crepidam", as set down by Pliny and later altered by other Latin writers to "Ne ultra crepidam judicaret", can be taken to mean that a shoemaker ought not to judge beyond his own soles. That is to say, critics should only comment on things they know something about. The saying remains popular in several languages, as in the English, "A cobbler should stick to his last", the Spanish, "Zapatero a tus zapatos", the Dutch, "Schoenmaker, blijf bij je leest", and the German, "Schuster, bleib bei deinen Leisten" (the last two in English, "cobbler, stick to your last").