'exogenous' originates from Greek, specifically the word 'exōgenēs,' where 'exō-' meant 'outside' and 'genēs' meant 'born or produced.'

'exōgenēs' transformed into the French word 'exogène,' and eventually became the modern English word 'exogenous' through scientific Latin.

Initially, it meant 'produced outside,' and this meaning has largely remained the same in modern usage.