From epha' (in the sense of hissing); an asp or other venomous serpent -- viper.
see HEBREW epha'
H660. epheh
אֶפְעֶה noun [masculine] a kind of viper (Thes 'a flando et sibilando;' compare Arabic viper, Ethiopic id.); — ׳א Isaiah 30:6; 59:5, א ׳לְשׁוֺן Job 20:16.