The Spanish word 'botijo', meaning 'earthen water jug', traces its origins back to Latin. It comes from the Latin word 'butticula', which meant 'small barrel'. This Latin word was itself a diminutive form, created by combining 'buttis' (meaning 'barrel' or 'cask') with the diminutive suffix '-culus'. The word evolved through Spanish 'botija' (meaning 'earthen jar') before taking its current form as 'botijo'.

This etymology shows how the meaning evolved from a general term for a barrel or cask, to specifically referring to a smaller vessel, and finally specializing to mean an earthen water jug in modern Spanish.

A closely related Spanish word is 'botija', which means 'earthen jar'. 'Botija' is actually the direct predecessor of 'botijo' and both words refer to similar clay vessels used for storing liquids. The main difference is that 'botijo' specifically refers to a water jug with a characteristic shape and spouts for drinking and filling.

While English doesn't have any direct cognates from the Latin 'buttis' that are commonly used today, the word 'butt' meaning 'a large cask or barrel' (as in 'wine butt') comes from the same Latin root, though this meaning is now rather archaic. The more familiar word 'bottle' is also distantly related, as it comes from the same Latin 'buttis' through Old French 'bouteille', which derived from the diminutive form 'butticula'.