ART, n. This word has no definition. Its origin is related by the ingenious Father Gassalasca Jape as "One day a wag - what would the wretch be at? Shifted a letter of the cipher RAT, And said it was a god's name! . . ."
Ambrose Bierce (2011). “Ambrose Bierce: The Devil's Dictionary, Tales, and Memoirs: The Devil's Dictionary, Tales, and Memoirs”, p.575, Library of America