The Spanish word 'autobús' comes from French 'autobus', which is a combination of two elements: the Greek prefix 'auto-' meaning 'self' and a shortened form of Latin 'omnibus' meaning 'for all'. The Latin 'omnibus' itself was formed from 'omnis' ('all') with the dative plural suffix '-ibus'. The term originally referred to a motorized vehicle for public transportation, with 'auto-' emphasizing its self-powered nature as opposed to horse-drawn carriages.

Some related Spanish words include 'auto' (car) and 'automóvil' (automobile), which share the same Greek prefix 'auto-' meaning 'self-moving' or 'self-powered'. The shortened form 'bus' is also commonly used in Spanish, just as in English.

English speakers will recognize many related words. 'Omnibus' still exists in English, though it's rather formal or old-fashioned, and gave us the shortened form 'bus'. The prefix 'auto-' appears in many English words like 'automobile', 'automatic', and 'autonomous', all carrying the sense of 'self' or 'self-operating'. The Latin 'omnis' meaning 'all' gives us English words like 'omnipotent' (all-powerful), 'omniscient' (all-knowing), and 'omnipresent' (present everywhere).