1977, originally a proprietary name, from jazz (n.) + ending from exercise (n.).
Entries linking to jazzercise
jazz n.
by 1912, American English, first attested in baseball slang; as a type of music, attested by 1915. Perhaps ultimately from slang jasm(1860) "energy, vitality, spirit," perhaps especially in a woman. This is perhaps from earlier gism in the same sense (1842).
By the end of the 1800s, "gism" meant not only "vitality" but also "virility," leading to the word being used as slang for "semen." But — and this is significant — although a similar evolution happened to the word "jazz," which became slang for the act of sex, that did not happen until 1918 at the earliest. That is, the sexual connotation was not part of the origin of the word, but something added later. [Lewis Porter, "Where Did 'Jazz,' the Word, Come From?" http://wbgo.org Feb. 26, 2018]
Meaning "rubbish, unnecessary talk or ornamentation" is from 1918. Slang all that jazz "et cetera" first recorded 1939. Further observations from Porter's summation of the research:
"Jazz" seems to have originated among white Americans, and the earliest printed uses are in California baseball writing, where it means "lively, energetic." (The word still carries this meaning, as in "Let’s jazz this up!") The earliest known usage occurs on April 2, 1912, in an article discovered by researcher George A. Thompson, and sent to me courtesy of [Professor Gerald ] Cohen.
... By 1915, jazz was being applied to a new kind of music in Chicago. It seems to have been first applied to Tom Brown's all-white band, which hailed from New Orleans. This was followed by many printed references to jazz as a musical style.
exercise n.
mid-14c., "condition of being in active operation; practice for the sake of training," from Old French exercice (13c.) "exercise, execution of power; physical or spiritual exercise," from Latin exercitium "training, physical exercise" (of soldiers, horsemen, etc.); "play;" in Medieval Latin also of arts, from exercitare, frequentative of exercere "keep busy, keep at work, oversee, engage busily; train, exercise; practice, follow; carry into effect; disturb, disquiet," from ex "off" (see ex-) + arcere "keep away, prevent; contain, enclose," from PIE *ark- "to hold, contain, guard" (see arcane).
The original notion in the Latin verb is obscure. Meaning "physical activity for fitness, etc." first recorded in English late 14c. Also from late 14c. as "a carrying out of an action; a doing or practicing; a disciplinary task." In reference to written schoolwork from early 17c. The ending was abstracted for formations such as dancercise (1967); jazzercise (1977); and boxercise (1985).