The Spanish word 'mes' (meaning 'month') comes directly from the Latin word 'mensis', which also meant 'month'. This is a straightforward evolution where the Latin word was simplified in Spanish by dropping the final '-is' syllable, a common pattern in the development from Latin to Spanish.

The word 'mes' is already one of the simplest and most common time-related words in Spanish. It appears in many common time expressions like 'mes a mes' (month by month) and 'cada mes' (every month).

English speakers might recognize the Latin root 'mensis' in words like 'menstrual' and 'menstruation', which relate to monthly cycles. The word 'semester' also contains this root - it originally meant 'six months' (sex = six + mensis = month). While English uses 'month' (which comes from Germanic origins) instead of a Latin-derived word, these technical and academic terms preserve the ancient Latin connection.