The Spanish word 'desvelado' (meaning 'sleepless' or 'awake') has an interesting formation from Latin roots. It starts with the Latin verb 'vigilare', meaning 'to stay awake' or 'to keep watch'. This evolved into the Spanish verb 'velar' (meaning 'to stay awake'). The modern word 'desvelado' is formed by adding the negative prefix 'des-' and the past participle suffix '-ado' to the stem 'vel-'. While you might expect a negative prefix to give an opposite meaning, in this case, 'des-' intensifies the sleeplessness, so 'desvelado' describes someone who is unable to sleep or is kept awake.

A simpler related Spanish word is 'velar', which means 'to stay awake' or 'to keep watch'. This is a more basic form without the prefix and suffix. You might also encounter 'vela' meaning 'vigil' or 'candle' (think of staying up by candlelight), and 'velador' meaning 'night watchman' - all these words share the common theme of wakefulness and watching.

English speakers might recognize a connection to words like 'vigilant', 'vigilance', and 'surveillance', which all come from the same Latin root 'vigilare'. These English words maintain the original sense of watchfulness and alertness. The connection becomes clearer when you consider that being 'desvelado' (sleepless) means you're forced to remain vigilant or awake when you'd rather be sleeping.