'lamentably' originates from the Latin word 'lamentabilis', where 'lamentari' meant 'to wail or mourn'.

'lamentabilis' transformed into the Old French word 'lamentable', and eventually became the modern English word 'lamentable', with 'lamentably' as its adverbial form.

Initially, it meant 'worthy of lament or sorrow', and this meaning has largely remained the same in modern usage.