The word COOL is from Yuruba ( West African language) and it was/is a serious cultural concept. Something fine, elegant, regal, perfect essense. For instance, it could describe a beautifully carved bead; it could describe behavior of the best kind.
The word came straight across the ocean into "cool jazz"...and has filtered into general American English. The word, and concept, are very cool. Overuse of it is not.
(I read this in a magazine article years ago. I love it!)
R