'accessorily' originates from the Latin word 'accessorius,' where 'access-' meant 'addition' and '-orius' was a suffix forming adjectives.

'accessorius' transformed into the Old French word 'accessoire,' and eventually became the modern English word 'accessory' through Middle English.

Initially, it meant 'something added,' but over time it evolved into its current meaning of 'in an accessory manner.'