1520s, from Middle French vipere, from Latin vipera "viper, snake, serpent," from vivus "alive, living" (see vital) + parere "bring forth, bear" (see pare). It formerly was believed (mistakenly) that the viper does not lay eggs. Applied to persons of spiteful character since at least 1590s. The only venomous snake found in Great Britain. Replaced native adder. "The flesh of the viper was formerly regarded as possessing great nutritive or restorative properties, and was frequently used medicinally" [OED]; hence viper wine, wine medicated with some kind of extract from vipers, used 17c. by "gray-bearded gallants" in a bid "to feele new lust, and youthfull flames agin."
