I chose to look up the term “jazz,” mostly because I was playing around with different terms on the Ngram viewer and was curious as to why there was a sudden sharp jump in the use of the word in the mid-1850s, only to disappear again a few years later and be practically nonexistent until its rise to popularity in the early 1900s.  Interestingly, it seems to have the same exact connotation as it does in modern times – everything that I found refers to a style of music.  I expected it to have shown up as some sort of popular slang term that was used for a little while and then forgotten about until it took on a new meaning, but as far as I could tell it’s always had the same one.  This raises another question that I couldn’t find the answer to – where did the term originally come from, and why would it be universally recognized for a few years, only to disappear for several decades before making a comeback?  One of the earliest sources that I could find was the pamphlet “Philosophy and Psychology” on Google Books, which is from 1855 (the year that the sudden upswing in use of the term began.)  It only discusses jazz for a few pages in reference to “higher” and “lower” forms of entertainment, but it seems to coincide with what we know as jazz today:

“If higher and lower have any meaning here, a man who cultivates jazz in preference to so-called good music, because he likes jazz better, ought really to cultivate the good music instead because it has more value. […]  In relation to any other state of his interests, or in case of his incapacity to develop this state, so-called good music does not have a higher value than jazz, and is not in any proper sense of the word ‘higher’.  It might be better for the man who actually prefers jazz to cultivate better music.  But it might not.” (page 53.)

This provides some intriguing, if confusing, insight.  It seems that jazz has something of a negative connotation here, while modern jazz is often considered a high-class, sophisticated form of music.  This implies that it might have once referred to a slightly different genre, or maybe that peoples’ view of it simply changed over time.  It’s odd that it only seems to be mentioned in this specific time frame while still being used the same way it is now, only to stop again so suddenly.  I wish that I’d been able to find more about where it might have come from, but for now I just have even more questions than when I started, even if this is interesting.