adder 1
/ad"euhr/ , n.
1. the common European viper, Vipera berus.
2. any of various other venomous or harmless snakes resembling the viper.
[ bef. 950; late ME; r. ME nadder ( a nadder becoming an adder by misdivision; cf. APRON), OE naeddre; c. OS nadra, OHG natara (G Natter ), ON nathra snake, Goth nadrs adder, OIr nathir snake, L natrix water snake ]
adder 2
/ad"euhr/ , n.
a person or thing that adds.
[ 1570-80; ADD + -ER 1 ]