'azulejo' originates from Spanish and Portuguese, specifically from Arabic 'al-zulayj' (الزلّيج), where 'al-' is the Arabic definite article and 'zulayj' meant 'polished stone' or 'small polished stone'.

'azulejo' changed from Arabic 'al-zulayj' into medieval Iberian forms (via Mozarabic influence) and was adopted into Old Spanish and Portuguese as 'azulejo', eventually becoming the modern Spanish and Portuguese term 'azulejo' used in English for the decorative glazed tile.

Initially it meant 'polished stone' (referring to small polished stones used in mosaics), but over time it evolved into its current meaning of 'glazed ceramic tile' used for architectural decoration.