The Spanish word 'cavidad' (meaning 'cavity') comes from the Latin word 'cavitas', meaning 'hollowness'. The Latin 'cavitas' was formed by combining two parts: the adjective 'cavus' meaning 'hollow', and the suffix '-itas' which was used to form abstract nouns indicating a quality or state. This combination literally described the quality or state of being hollow, which evolved into the modern Spanish word for a cavity or hollow space.

Several common Spanish words share this root, including 'cava' (cave or cellar), 'cavar' (to dig), and 'concavo' (concave). All these words relate to the basic concept of hollowness or empty space, showing how the ancient Latin root 'cavus' has influenced various Spanish words describing hollow spaces or the action of creating them.

English speakers might recognize this etymology in words like 'cave', 'cavity', 'concave', and 'excavate'. All these words share the same Latin ancestor 'cavus'. The English word 'cavity' is particularly close to the Spanish 'cavidad', as both came from Latin 'cavitas' and retained very similar meanings, referring to a hollow space or hole.