The Spanish verb 'gastar' (meaning 'to spend' or 'to wear out') comes from the Latin verb 'vastare', meaning 'to lay waste' or 'devastate'. This Latin verb was derived from the adjective 'vastus', meaning 'empty' or 'desolate'. The semantic evolution from 'laying waste' to 'spending/wearing out' makes intuitive sense - when you spend money or wear something out, you are in a way depleting or 'laying waste' to your resources. The initial 'v' sound in Latin evolved into 'g' in Spanish, which is a common sound change between these languages.

Some related Spanish words include 'gasto' (expense, cost), 'gastador' (spender), and 'desgastar' (to wear down, erode). All these words share the core meaning of depleting or using up resources.

The English word 'vast' comes from the same Latin root 'vastus', though it developed a different meaning. While in Spanish the focus went toward the idea of depleting resources, in English the meaning evolved to emphasize the 'empty' aspect of 'vastus', leading to our modern sense of 'vast' as something extremely large or extensive. The English word 'devastate' is also related, coming from Latin 'devastare' (de + vastare), and maintains a meaning closer to the original Latin sense of 'laying waste'.