"If the truth were known about the origin of the word 'Jazz' it would never be mentioned in polite society." ["Étude," Sept. 1924]The verb meaning "to speed or liven up" is from 1917; all that jazz "et cetera" first recorded 1939; Jazzercise is 1977, originally a proprietary name. Jazz Age first attested 1922 in writings of F. Scott Fitzgerald, usually regarded as the years between the end of World War I (1918) and the Stock Market crash of 1929.