The Spanish word 'barriga' meaning 'belly' comes from the Celtic word 'barrica', which referred to a belly-shaped container or barrel. This is a clear example of how physical resemblance influenced the development of language - the round, protruding shape of a barrel was metaphorically extended to describe the human belly.

A related Spanish word is 'barrica' (barrel), which maintains the original Celtic meaning. Another related word is 'barril' (barrel). These words share the same conceptual connection to rounded, container-like shapes.

While not directly related through Celtic, English speakers might find it interesting that the word 'barrel' has a similar conceptual connection, though it came into English through Old French 'baril'. The similarity in form and meaning between Spanish 'barriga' and English 'barrel' can help English speakers remember the Spanish word for belly.