'viper's' is the possessive form of 'viper', which originates from Old French, specifically the word 'vipere', from Latin 'vipera', where 'vi-' meant 'alive' and 'parere' meant 'to bear (give birth)'.

'vipera' transformed into the Old French word 'vipere', and eventually became the modern English word 'viper'. The possessive form 'viper's' is created by adding an apostrophe and 's' to the noun.

Initially, 'vipera' referred to a type of snake, and the possessive form simply indicated ownership or association. This meaning has remained consistent.