'dissimilarity' originates from Latin, specifically the word 'dissimilitudo,' where 'dis-' meant 'apart' and 'similis' meant 'like or similar.'

'dissimilitudo' transformed into the French word 'dissimilarité,' and eventually became the modern English word 'dissimilarity' through Middle English.

Initially, it meant 'the quality of being unlike,' and this meaning has largely remained the same in modern usage.