נָחוּשׁnâchûwshStrong's H5153

coppery, i.e. (figuratively) hard

Derivation: apparently passive participle of נָחַשׁ (H5172) (perhaps in the sense of ringing), i.e. bell-metal; or from the red color of the throat of a serpent (נָחָשׁ (H5175), as denominative) when hissing)