…what the word "jazz" meant back when it was not considered respectable.
A lot has been written by people trying to fix the origin of the word jazz. I don't intend to deal with all of that. My perspective has become that in the late 1800s and early 1900s within the USA the word should be recognized as having different sociological and mixed cultures' context
For example when a New Orleans band went to Chicago the local musicians union tried to keep people from patronizing the outsiders by decrying it as Jass/Jazz. At that time a large Chicago population base was from what generally was called Germany. These included craft makers who had apprenticed and sojourned for work; these were known as journeyman which for purposes here translates into
unter.
There was a mid-1800s European card game called
JASS and in Bavaria (located in modern Germany) their style of deck since 1865 had a suit (equivalent to the suit of clubs) that had the image for an
unter shown below. Being a man myself I can readily imagine how hard living fellows pulling certain cards out crudely sexualized it's context leading to
jass (jazz) becoming part of Chicago slang initially among carpenters, carvers, roofers, instrument makers and other working class poor.
However, I think there is a valid reason to think that in New Orleans the usage of Jazz arose differently considering it being an early international port with French language linkage. A French word for dance
chassé would have been part of visiting mixed nationality sailors' polyglot vocabulary without their pronunciation always being precise; this sounded out by New Orleans' mixed English speaking population as "jazz". [This is not my original idea just a summarization.]
As for the west coast of USA it is worth remembering that for decades San Francisco was reached by sea and not in any economic sense overland. And for that matter it had it's own early jazz era musicians/venues when jazz was music for dancing not a recital event.
Printed early usage of the word jazz for California can be found before 1900 referring to sportsman with a connotation of attitudinal ability (baseball jargon 'pep'). One writer contends it was borrowed from usage pertaining to women without suggesting any insinuation. Again, San Francisco being an international port I can imagine it's meaning of liveliness derives from when new dances called
chassé were introduced leading to Anglicized pronunciation approximating the sound "jazz."
In closing: it seems to me that it was after the New Orleans bands exposure to Chicago that
jass -> jazz spread as slang for "disrespect-able" activity into the more southern regions. And it was the maritime USA dynamics which spread
chassé -> jazz.