Plural of coolness; instances or degrees of being cool in temperature, or qualities of emotional detachment and composure.
From 'cool' plus the suffix '-ness' to form an abstract noun, then pluralized. The plural form suggests multiple instances or manifestations of the quality of coolness.
The plural 'coolnesses' is rare because 'coolness' is already abstract—we don't usually pluralize abstract qualities, but technically you could describe 'the different coolnesses of metal versus plastic,' making it valid.
Complete word intelligence in one call. Free tier — 50 lookups/day.