“The deaf adder stoppeth her ears, and will not hearken to the voice of the charmer, charm he never so wisely” (Psalm lviii. 4, 5). Captain Bruce says, “If a viper enters the house, the charmer is sent for, who entices the serpent, and puts it into a bag. I have seen poisonous vipers twist round the bodies of these psylli in all directions, without having their fangs extracted.” According to tradition, the asp stops its ears when the charmer utters his incantation, by applying one ear to the ground and twisting its tail into the other. In the United States the copperhead is so called.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894