viper [E16th] Some vipers give birth to live young which have hatched from eggs within the parent’s body, whereas the eggs of most snakes are laid before they hatch. The name viper derives from the fact they are viviparous (‘producing live young’ M17th), coming from Latin vivus ‘alive’, as in vivisection [E18th], and parere ‘to bring forth’, the source of parent [LME]. See also adder, snake.