English
enharden
From en- + harden, with en- as an intensifying prefix.
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
verb To harden; to render hard.
Language periods are conventional ranges, not dates for this word.
Etymograph / enharden