'happily' originates from Middle English, specifically the word 'hap,' where 'hap' meant 'chance' or 'fortune.'

'hap' transformed into the Old English word 'happ,' and eventually became the modern English word 'happy,' from which 'happily' is derived.

Initially, it meant 'by chance or luck,' but over time it evolved into its current meaning of 'in a happy manner.'