- 1: moderately cold : lacking in warmth
- 2a : marked by steady dispassionate calmness and self-control <a cool and calculating administrator — Current Biography>b : lacking ardor or friendliness <a cool impersonal manner>c of jazz : marked by restrained emotion and the frequent use of counterpoint d : free from tensions or violence <we used to fight, but we’re cool now>
- 3—used as an intensive <a cool million dollars>
- 4: marked by deliberate effrontery or lack of due respect or discretion <a cool reply>
- 5: facilitating or suggesting relief from heat <a cool dress>
- 6a of a color : producing an impression of being cool; specifically : of a hue in the range violet through blue to green b of a musical tone : relatively lacking in timbre or resonance
- 7slang a : very good : excellent; also : all right b : fashionable, hip <not happy with the new shoes … because they were not cool — Celestine Sibley>
“Cool.” Merriam-Webster.com. Merriam-Webster, n.d. Web. 1 June 2016.
In 1933 the word “cool” went from cool in temperatures to slang for fashionable in African American Vernacular which is the closest to how we use our clang today. The word first started to change in descriptions on an emotional level, i.e. having a cool head versus a hot head and described self control. The word itself has Dutch and German origins. The word originally was spelled as “col” and like most words, the spelling changed periodically for years after.
“But starting around the 1930s, cool began appearing in American English as an extremely casual expression to mean something like ‘intensely good.’ This usage also distinguished the speaker, italicizing their apartness from mainstream culture. As its popularity grew, cool’s range of possible meanings exploded. Pity the lexicographer who now has to enumerate all the qualities collecting in the hidden folds of cool: self-possessed, disengaged, quietly disdainful, morally good, intellectually assured, aesthetically rewarding, physically attractive, fashionable, and on and on.”
Shakespeare used the word in several plays,
In Shakespeare’s A Midsummer Night’s Dream, Theseus tells Hippolyta:
“Lovers and madmen have such seething brains,
Such shaping fantasies, that apprehend
More than cool reason ever comprehends.”
Hamlet, disheveled and ranting at the ghost of his dead father, frightens his mother, Gertrude, who cries out “O gentle son, Upon the heat and flame of thy distemper Sprinkle cool patience.”
The RJ Reynolds tobacco company, the same company responsible for cool Joe Camel was the first to use Cool in advertisement to describe something other than temperature. The company took their own spin on things can made “Kool” menthol cigarettes in 1933, still produced today.
By the 1940’s, “Cool Cat” was a common term in the American Jazz scene, and while “Cool Cat” is not said anymore, “Cool” is used daily by many people and is in regards to being fashionable and laid back.
This is a Cool post on the history of the word from Slate.
Skinner, D. (2014). the rise of cool. Humanities, 35(4), 32-37.
Brief History of American Slang 
