'undoubtedly' originates from the word 'undoubted,' which is derived from the prefix 'un-' meaning 'not' and 'doubted,' which comes from the Latin word 'dubitare,' meaning 'to doubt.'

'undoubted' changed from the Old French word 'douter' and eventually became the modern English word 'undoubted.'

Initially, it meant 'not doubted,' but over time it evolved into its current meaning of 'certainly.'