The Spanish word 'cuando' (meaning 'when') comes from the Latin word 'quando' (meaning 'when, at what time'). The Latin 'quando' itself was formed by combining two elements: 'quam' (meaning 'how, as') and the locative particle '-do'. This combination created a word that specifically referred to time, transforming the general interrogative sense of 'how' into a temporal one.

While 'cuando' is already one of the most basic and common Spanish words, you might encounter it in common combinations like 'de cuando en cuando' (meaning 'from time to time') or 'cuando quiera' (meaning 'whenever').

While English 'when' is not directly related to Spanish 'cuando', we can see a similar pattern in how both languages formed their temporal interrogative words. The Latin 'quam' that forms part of 'cuando' is actually related to English words like 'quantity' and 'quality', which also deal with asking about the nature or measure of things, though they've evolved to have more specific meanings.