Youngsters today use 'cool' as an everyday term of approval or assent. Our teen was quite surprised, some years ago, to find that her parents' generation regarded this as a quaint revival of a term we associated with jazz musicians of a bygone age.We await the revival of 'hip' or 'hep': can that be far behind? So when did the jazz fraternity first use 'cool'?

And what of 'cat' ? 'Hep'/'hip' or 'cool' and 'cat' often fell together but only ever sounded right if the speaker was black, wearing shades , in a dark room and holding a sax . So when did that word 'cat' first come to be used of a jazz man ?

(Some words never die but merely fade away. So in the 60s young men would talk of a 'bird' when referring to a young woman. This word for a young woman had been used hundreds of years ago but suddenly reappeared as a new term. And the current British vogue word 'chav', for a certain type or style of working class man or woman, has its origins in a Romany word used by Londoners of a seasonal worker in the hop fields of Kent )

At least 1933, according to etymology online:
Slang use for "fashionable" is 1933, originally Black English, said to have been popularized in jazz circles by tenor saxophonist Lester Young

Lester young was only one of many to use the terms you describe.

Both Duke Ellington and Cab Calloway used these terms ,both in their music but also to describe it or to introduce a tune to their audience before playing it.

These terms were used by Black and White musicians alike.

Another term used constantly was the term "Man".

It was used because many musicians couldn't remember someone else's name.They would also not hesitate to call a woman "Man" .It was a term of endearment ,a way of recognizing another jazz musician or a follower of jazz music.

The term "Hep Cat" came first ,followed shortly after with the term"Hip Cat" ,followed by just the word"Hip" to describe anyone who was knowledgeable about Jazz Music.

In the twenties and thirties jazz was described as"Hot",with the advent of Bebop the term became"Cool".

All of these words were originally coined by musicians to describe their music and was sort of an insiders language used only by musicians and lovers of Jazz.Eventually the general public began to use some of these terms.

hippolips

"Hep" lasted about a year, before it became co-opted by white musicians, many of whom had no clue about Jazz. "Hip" has lasted for decades.


White male college student, speaking to black musician circe 1935: I'm hep to your music, man

Black musician, sarcastically: I'm hip that your hep.

The Cool School of Jazz came out of the Bebop of the 1940s. The Cool School's time period was roughly synchronous with the Beat Era, which evolved into the Hippie Era. (A short time after this, Miles Davis left the planet for parts unknown.)

I recall one source (either Bill Bryson in "The Mother Tongue" or the PBS series "The Story of English") saying that "hep cat" came from an African word, "hepicat". I don't buy it.