The Spanish word 'cojones' (meaning 'testicles') has an interesting journey through ancient languages. It started with the Ancient Greek word 'koleos', which meant 'sheath' or 'scabbard'. This word was borrowed into Latin as 'coleus', where its meaning shifted to specifically refer to 'testicle'. The word then evolved in Vulgar Latin to 'coleo', maintaining the same meaning.

As the language continued to develop into Spanish, 'coleo' transformed into 'cojón' (singular) and 'cojones' (plural). The change from 'l' to 'j' is a common sound change in Spanish evolution from Latin. Today, 'cojones' is often used figuratively to mean 'courage' or 'bravery' in Spanish slang, similar to how English uses other anatomical terms metaphorically for bravery.

While 'cojones' itself is a commonly known Spanish word, it doesn't have many etymologically related words in modern Spanish that would be considered simpler or more formal. The singular form 'cojón' and some derivative forms exist, but they all maintain similar meanings and levels of formality.

While English has borrowed the word 'cojones' directly from Spanish (particularly in American English slang), there aren't any common English words that are etymologically related through the Greek or Latin roots. The original Greek word 'koleos' did give us the scientific term 'coleoptera' (the order of beetles), where it refers to the hardened wing cases that act as a 'sheath' for beetles' wings, but this is a highly specialized technical term.