PICAYUNE, the name in Florida and Louisiana of the Spanish half-real, = ^ of a dollar, 6 cents, and hence used of the United States 5 cent piece. The French picaillon, from which the word was adapted in America, was an old copper coin of Piedmont.
Is origin is doubtful, but is possibly related to the Italian piccolo, ittle, small. In America the word is used of anything trifling, petty, mean or contemptible.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)