English
hellacool
hella + cool
Proto-Indo-European *gel- ‘to be cold, to freeze’
…
Proto-Germanic *kōluz ‘cool’
Proto-West Germanic *kōl(ī)
Old English cōl ‘cool, cold, calm’
Middle English cool
English cool
Today it means
adj Very cool (fashionable or excellent).
Language periods are conventional ranges, not dates for this word.
Etymograph / hellacool