English
hardener
From harden + -er.
A compound of harden + -er
Proto-Germanic *harduz ‘hard’
…
Proto-West Germanic *hardēn ‘to become hard, harden, solidify’
Old English heardian ‘to be or become hard’
Middle English harden
Middle English hardenen
English harden
Today it means
noun One who, or that which, hardens.
Language periods are conventional ranges, not dates for this word.
Etymograph / hardener