'eunuch' originates from Greek, specifically the word 'εὐνοῦχος' (eunoukhos), where 'eune' meant 'bed' and the element '-ekhos/ -oukhos' related to 'holding' or 'guarding'.

'eunuch' changed from the Greek 'εὐνοῦχος' into Latin as 'eunuchus', passed through Medieval Latin and Old French/Middle English forms, and eventually became the modern English word 'eunuch'.

Initially it meant 'bed-keeper' (a guardian of women's quarters), but over time it came to mean 'a castrated man, especially a court official,' and later acquired a figurative sense of 'a person deprived of power or effectiveness'.