The Spanish word 'petrolero' comes from combining 'petróleo' (meaning petroleum) with the suffix '-ero' which is used to indicate an occupation or relationship to something. 'Petróleo' itself comes from the Latin word 'petroleum', which literally meant 'rock oil' or 'oil from stone'. This Latin word was formed by combining 'petra' (meaning stone) and 'oleum' (meaning oil). This name was given because petroleum was often found seeping from between rocks or underground stone formations.

Some simpler related Spanish words include 'petróleo' (petroleum/oil) and 'piedra' (stone, from the same Latin root 'petra'). The suffix '-ero' is very common in Spanish and appears in many occupation words like 'panadero' (baker), 'carpintero' (carpenter), and 'jardinero' (gardener).

English speakers can recognize the connection to words like 'petroleum', 'petrol' (British English for gasoline), and 'petrified' (turned to stone). The Latin 'oleum' gives us English words like 'oil' and 'oleic'. The word 'petra' meaning stone also appears in English words like 'petrify' (to turn to stone) and 'petrology' (the study of rocks).