The Spanish word 'inútil' (meaning 'useless') comes directly from the Latin word 'inutilis', which had the same meaning. The Latin word was formed by combining two parts: the prefix 'in-' meaning 'not' and the word 'utilis' meaning 'useful'. This is a straightforward example of how adding 'in-' to a word creates its opposite meaning - literally 'not useful' became 'useless'.

The word maintained its form and meaning remarkably well as it evolved from Latin to Spanish, with only slight changes in pronunciation and the addition of an accent mark on the 'ú'.

A simpler related Spanish word is 'útil', meaning 'useful', which comes from Latin 'utilis'. You can see how 'inútil' is simply 'útil' with the negative prefix 'in-' added to it. Other related Spanish words include 'utilidad' (utility), 'utilizar' (to use), and 'utilitario' (utilitarian).

English speakers can easily connect 'inútil' to several English words that share the same Latin roots. The most obvious ones are 'utility' and 'utilize', both from the same Latin root 'utilis'. The English word 'inutile' (though rare) is a direct cognate. The prefix 'in-' works the same way in English as in Spanish, creating negatives like in words such as 'inactive', 'incorrect', and 'invisible'.