The Spanish word 'vago' has two main meanings that come from two different Latin sources. The first meaning, 'idle' or 'unoccupied', comes from the Latin word 'vacuus' meaning 'empty' or 'unoccupied'. The second meaning, 'wandering', comes from the Latin word 'vagus' which also meant 'wandering'. Over time, these two Latin words merged in Spanish to create the modern word 'vago', which can carry both meanings depending on context.

Some related Spanish words include 'vacante' (vacant, empty) and 'vagabundo' (vagabond, wanderer), which share the same Latin roots. 'Vacante' comes from 'vacuus' and refers to an empty position or space, while 'vagabundo' comes from 'vagus' and refers to someone who wanders without a fixed home.

English speakers might recognize the connection to several familiar words. From 'vacuus', we get words like 'vacant', 'vacation' (originally meaning to leave empty), and 'vacuum'. From 'vagus', we get words like 'vague' (originally meaning wandering or straying), 'vagabond', and even 'vagrant'. The connection between wandering (physically or mentally) and emptiness can be seen in both Spanish and English derivatives.