sesquipedalian

Horace, the ancient Roman poet known for his satire, was merely being gently ironic when he cautioned young poets against using sesquipedalia verba—"words a foot and a half long"—in his book Ars poetica, a collection of maxims about writing. But in the 17th century, English literary critics decided the word sesquipedalian could be very useful for lambasting writers using unnecessarily long words. Robert Southey used it to make two jibes at once when he wrote "the verses of [16th-century English poet] Stephen Hawes are as full of barbarous sesquipedalian Latinisms, as the prose of [the 18th-century periodical] the Rambler." The Latin prefix sesqui- is used in modern English to mean "one and a half times," as in sesquicentennial (a 150th anniversary).