The Spanish word 'azul' (meaning 'blue') has a fascinating journey that starts in ancient Sanskrit. It originated from the Sanskrit word 'rajavarta', meaning 'king's curl', which was used to describe the precious stone lapis lazuli. This term made its way into Persian as 'lažvard', still referring to lapis lazuli, and then into Arabic as 'lāzaward'. The word continued to evolve in Andalusi Arabic (the Arabic spoken in medieval Islamic Spain) as 'lazawárd', before becoming 'azur' in Old Spanish and finally 'azul' in modern Spanish.

This etymology shows how the word transformed from describing a specific blue gemstone (lapis lazuli) to becoming the general word for the color blue in Spanish. The initial 'l' was lost over time as the word was adapted into Spanish, and the meaning broadened from the specific blue of lapis lazuli to encompass all shades of blue.

The Spanish word 'añil' (meaning 'indigo') is related to 'azul' through a similar Arabic origin, though it came through a different path. Both words ultimately refer to blue pigments or dyes used in ancient times.

English speakers might recognize the connection to the word 'azure', which comes from the same Arabic source through Old French. 'Azure' in English specifically refers to a bright, sky-blue color, preserving a more specific meaning than the general 'blue' meaning of Spanish 'azul'. The word 'lazuli' in 'lapis lazuli' is also related, maintaining a direct connection to the Persian and Arabic terms for this blue gemstone.