Initially I thought "cool" might have its staying power because it's the baseline... the first word to really encapsulate a concept (perhaps defined as "innovat

Initially I thought "cool" might have its staying power because it's the baseline... the first word to really encapsulate a concept (perhaps defined as "innovatively unique")... and the others are just knock-offs trying to redefine the standard. but I'm pretty sure "hep" would be considered a synonym of cool that predates it. So why didn't "hep" become the everlasting "cool" word?