'calamitous' originates from Latin, specifically the word 'calamitosus,' where 'calamitas' meant 'damage or disaster.'

'calamitosus' transformed into the Old French word 'calamiteux,' and eventually became the modern English word 'calamitous' through Middle English.

Initially, it meant 'causing damage or disaster,' and this meaning has largely remained the same in modern usage.