Cool has its roots in Middle English "cole", from Old English "col" and indicates aloofness, composure and absence of excitement in a person, especially in times of stress.
The usage of cool as a general positive epithet or interjection has been part of English slang since World War II, and has been incorporated into other languages, such as French and German. Use of the term in this manner has its origin in African-American slang, in which, among other things, it can mean "excellent", "intriguing", or "superlative," having first been recorded in written English in the early 1930s. (See Cool (aesthetic).)
Cool can also be: