The Spanish word 'nocturno' (meaning 'nocturnal') comes from the Latin word 'nocturnus', meaning 'of the night'. The Latin 'nocturnus' was formed by combining two elements: the root 'nox' meaning 'night', and the suffix '-urnus' meaning 'belonging to'. So literally, the word was built to mean 'belonging to the night'.

Some related Spanish words that might be more familiar include 'noche' (night), which comes from the same Latin root 'nox'. You can also find this root in words like 'anoche' (last night) and 'medianoche' (midnight). Understanding this connection can help you remember that 'nocturno' refers to things relating to or occurring during the night.

English speakers can easily relate 'nocturno' to several similar English words that share the same Latin origin. These include 'nocturnal' (active at night), 'nocturne' (a musical composition inspired by or evocative of night), and 'equinox' (when night and day are equal length). The 'noct-' element in all these words carries the meaning of 'night' from the original Latin 'nox'.