The Spanish word 'macho' comes from the Latin word 'masculus' meaning 'male' or 'masculine'. 'Masculus' itself was formed by combining the Latin root 'mas' (meaning 'male') with the diminutive suffix '-ulus'. Over time, as Latin evolved into Spanish, 'masculus' underwent sound changes to become 'macho', while retaining its core meaning of 'male'.

In Spanish, there are several related words that share this etymology, including 'masculino' (masculine) and 'másculo' (manly), which are more formal variants that stayed closer to the original Latin form. These words all emphasize different aspects of masculinity or maleness.

English speakers might recognize the connection to words like 'masculine', 'male', and even 'masculinity', which all trace back to the same Latin root 'masculus'. The English word 'macho' itself was borrowed directly from Spanish and has come to specifically refer to an exaggerated or aggressive form of masculine pride or behavior.