The Spanish word 'eunuco' (meaning 'eunuch') comes from Latin 'eunuchus', which was borrowed from Ancient Greek 'eunouchos'. The Greek word is actually a compound of two elements: 'eune' meaning 'bed' and a form of 'ekho' meaning 'to keep or guard'. So literally, a 'eunouchos' was a 'bed-keeper' or 'bedroom guardian' - this referred to trusted servants who were castrated and put in charge of guarding the women's quarters in royal households and harems of ancient times.

There aren't many common Spanish words directly related to 'eunuco' since it comes from a very specific Greek compound word that wasn't widely used to form other terms.

The English word 'eunuch' is directly related to Spanish 'eunuco', as they both come from the same Greek source 'eunouchos'. The words maintain almost identical spelling and meaning across both languages, making it easy to remember. You might also encounter this word in historical dramas or documentaries about ancient royal courts where eunuchs played important roles.