'justifiably' originates from the Latin word 'justificare', where 'justus' meant 'just' and 'facere' meant 'to make'.

'justificare' transformed into the Old French word 'justifier', and eventually became the modern English word 'justify', from which 'justifiably' is derived.

Initially, it meant 'to make just or right', but over time it evolved into its current meaning of 'in a manner that can be shown to be right or reasonable'.