I knew about the baseball connection with "jazz", but there are also supposed to be indications that the word was already in use in the jazz community in New Orleans (where there were strong interactions between Black and Irish immigrant musicians), and that was apparently just the first time it appeared in print. Still, I agree that it's all just theory, and we'll probably never know.
Just one caution as to the etymologies in dictionaries, even the venerable OED. When it comes to some words in English, the etymologies given in order to tie them to proto-Indo-European roots can be very strained. As I've mentioned before, there is a (still disputed by some) theory that up to a third of the basic Germanic vocabulary comes from a pre-Indo European "substrate" which was found in Northern Europe when the proto-Indo-European speakers arrived there, but none of the major dictionaries seem willing even to admit the possibility, so they often propose very tenuous proto-Indo-European origins for words. Tellingly, etymologies sometimes stop at some early stage of Germanic and go no further back. That can mean (though it does not necessarily have to mean) that the etymologist couldn't come up with even a strained connection from that point to proto-Indo-European.
Please don't confuse what I'm saying here with the debate that occurred on the forum recently about origins of words in the pre-Indo-European language(s) spoken in the Balkan area. There are certainly traces of substrates in most languages,including Greek (place names ending in
-ossos, for example, like
Knossos), and it only makes sense that some traces of earlier languages do survive when a new "prestige" language takes over. What I'm talking about, though, is a specific theory as to the Germanic languages, where there are indications that the incoming proto-Indo-European speakers came into contact with a culture which engaged in sea-faring and had other attributes, such as a formal kingship, for which the incomers did not have adequate terminology, and where a significant portion of the older terminology survived. The classic examples are sea-faring words like
boat, ship and
sail; the cardinal directions,
North, South, East, and
West; titles like
king; and some colors, such as
blue. The Germanic words for these things are arguably not of Indo-European origin (please note that I said "arguably").
And, before anyone objects to say that those names for the cardinal directions, and even the color name
blue, are also shared by some Romance languages, please note that it's historically fairly clear that those languages adopted those words from Germanic invaders, though not all in the same form or to the same extent. For example, the words
bleu and
blu made it into French and Italian, but
azul (of Latin origin) survived in Spanish. And also, lest someone propose that Irish
bád shows that
boat has an Indo-European origin, note that
bád (like
seol for
sail) is believed to have come into Irish from Norse (a Germanic language), in the same way that
long did. Of course, it might also have come from an Irish substrate that was related to the same substrate at work in the Germanic languages. We will probably never really know, unless some aliens who visited us milennia ago kept good records and can tell us more.
