The Spanish word 'muchacho' (meaning 'boy') has an interesting etymology that traces back to the Latin word 'mutilus', meaning 'mutilated' or 'cropped'. This evolved into the Spanish word 'mocho', meaning 'cropped' or 'shorn'. From 'mocho', the Old Spanish term 'mochacho' developed, which then evolved into the modern Spanish 'muchacho'. The semantic shift from a word meaning 'cropped/shorn' to meaning 'boy' likely developed from the practice of young boys having their hair cut short.

A simpler related Spanish word is 'mocho', which is still used today to mean 'cropped' or 'cut off'. While 'muchacho' came to specifically refer to a boy or young man, its etymological cousin 'mocho' retained its original meaning related to something being cut or shortened.

While there aren't any commonly used English words that are directly related to 'muchacho', the Latin root 'mutilus' did give English the word 'mutilate', though this carries a much more severe meaning than the original Latin term. This shows how words from the same root can evolve to have very different meanings across languages.