'isomerous' originates from Greek, specifically the word 'isomēros,' where 'iso-' meant 'equal' and 'meros' meant 'part.'

'isomerous' changed from the Late Latin word 'isomerus,' which came from Greek 'isomēros,' and eventually became the modern English word 'isomerous.'

Initially, it meant 'having equal parts,' but over time it evolved into its current meaning of 'having an equal number of parts or organs, especially in each whorl of a flower.'