hardi

the past participle of the archaic verb hardir, which gave rise to the current enhardir; hardir corresponds to the Old High German hartjan ('to harden, to make strong'), from the Old High German harti ('hard, in reference to things; strong, bold, in reference to people'). Grimm's law directly relates harti to the Sanskrit kratu, 'the one who accomplishes' and also 'power'; it is the Greek adjective meaning 'strong'.