The Spanish word 'vela' has multiple distinct etymological origins, which explains its different meanings. The first meaning, 'candle' or 'watchfulness', comes from the Latin 'vigilare' meaning 'to keep watch', which itself derives from 'vigil' meaning 'watchman'. This connection makes sense as candles were historically used to keep watch through the night.

A second meaning of 'vela' meaning 'sail' (as in a ship's sail) comes directly from the Latin word 'velum' meaning 'sail' or 'curtain'.

In Andalusian Spanish, 'vela' can also mean 'somersault', which comes from the Latin 'voluta' meaning 'turn' or 'roll'.

Several common Spanish words are related to 'vela'. The verb 'velar' means 'to stay awake' or 'to watch over', sharing the same Latin root 'vigilare'. 'Vigilar' meaning 'to watch over' or 'to guard' is another related word that more closely preserves the original Latin form. The word 'velador' meaning 'nightstand' or 'night watchman' is also related, referring to either a piece of furniture that holds a candle or a person who keeps watch.

English speakers might recognize the connection to several familiar words. 'Vigil' and 'vigilant' come from the same Latin root as the 'candle/watchfulness' meaning of 'vela'. The English word 'veil' is related to the 'sail' meaning of 'vela', both coming from Latin 'velum'. The word 'volute', meaning a spiral scroll-like ornament, shares its origin with the 'somersault' meaning of 'vela', both coming from Latin 'voluta' meaning to turn or roll.