'anadidymus' originates from Greek, specifically the word 'anadidymos,' where 'ana-' meant 'together' and 'didymos' meant 'twin' or 'testicle.'

'anadidymos' was adopted into New Latin as 'anadidymus' in medical terminology, and eventually became the modern English word 'anadidymus.'

Initially, it meant 'fused twins' or 'fused testicles,' and this meaning has remained specific to the medical context in modern usage.