Denominative from 'iysh; to be a man, i.e. Act in a manly way -- show (one) self a man.
see HEBREW 'iysh
[אשׁשׁ] (compare found, establish)
Hithpo`el וְהִתְאשָׁ֑שׁוּ Isaiah 46:8 (derived from above by ᵑ7 Jerome Hi Kn De MV, shew yourselves firm, but) read perhaps הִתְבּשָׁ֑שׁוּ Lag Che, see בּוֺשׁ (Thes explanation as denominative from אִישׁ; on other views compare Di).