* Old English "cūl": This word meant "cold," and its origins are thought to be related to the Proto-Germanic word *kūlaz.
* 16th Century: The word "cool" started to be used more broadly, encompassing ideas of calmness, composure, and even fashion.
* Mid-20th Century: The word "cool" took on its modern, slang meaning of being fashionable, impressive, and desirable. This usage was popularized by jazz culture in the 1950s.
So, while the original "cool" was borrowed from Old English, the word's modern meaning came about through a long process of evolution and cultural shifts.