H5153 נָחוּשׁ

coppery, i.e. (figuratively) hard

of brass.

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