The Spanish word 'gasto' (meaning 'expense' or 'spending') comes from the Spanish verb 'gastar' (meaning 'to spend'), which in turn derives from the Latin word 'vastare' meaning 'to devastate' or 'lay waste to.' The semantic evolution from 'to devastate' to 'to spend' reflects how spending money can be seen as depleting or diminishing resources, similar to how devastation depletes an area of its resources.

A closely related and very common Spanish word is the verb 'gastar' (to spend), from which 'gasto' is directly derived. You might also encounter words like 'gastador' (spender) and 'gastos' (expenses, costs) in the same word family.

While there aren't many common English words directly related to 'gasto,' we do have some words that share the Latin root 'vastare,' such as 'vast' and 'devastate.' These words maintain the original Latin sense of something being made empty or laid waste to, while the Spanish words took on the more specific meaning of depleting financial resources.