Jazz / Jass
The OED lists the earliest print usage of "Jazz," originally a dance and not, as in current use, the musical form, as 1909. The exact dating of this episode is unclear, though it seems likely to have occurred earlier. The usage is not anachronistic though its precise usage(as a musical form rather than a dance)may be unknown. As for the unusual spelling, the OED lists "Jass" as a variant, though with no information as to where or when it was prevalent. see OED article above.
In my music student days, I was told Jazz was a Creole word. It's no secret that the Empire builders made sure to extirpate or pervert language and culture from countries under their protection. (See discussion of Tartan on pg. 220) Not that one shouldn't trust the OED, but it is an ENGLISH DICTIONARY. New Orleans was the third largest disembarkation port for poor Irish fleeing An Gorta Mor (or 'Famine' as some would have it) They came as ballast on returning trans-Atlantic cotton ships. They liked N.O. because it was a Catholic city and the City Fathers liked them because they worked for next to nothing on projects like the New Basin Canal and were also content to work and live with the Black population. Quite a few slang words came into American English from the original Irish (galore, baloney (as in foolish talk, not meat), bunkum, hoodoo, spiel, and those gangster words for face and mouth: pus and gob!) There is an Irish language word spelled teas in Irish letters and pronounced tjazs in our letters. It suggests excitement or passion and could be connected to the blend of dance that led from Irish step to American tap.
I learned today of a book, How the Irish Invented Slang:The Secret Language of the Crossroads by Professor Dan Cassidy  which I'm sure has these and more.