The Spanish word 'vaquero' (meaning 'cowboy') comes from combining two elements: the Spanish word 'vaca' (meaning 'cow'), which derives from Latin 'vacca' (also meaning 'cow'), and the Spanish suffix '-ero' which is used to form nouns indicating a person's occupation or profession. So literally, a 'vaquero' is 'one who works with cows' - a cowboy or cattle herder.

The most obvious related Spanish word is 'vaca' (cow), which is simpler and more commonly encountered than 'vaquero'. This is the base word to which the occupational suffix '-ero' was added. You'll find this same pattern in many Spanish occupational terms, like 'panadero' (baker, from 'pan' meaning bread) or 'jardinero' (gardener, from 'jardín' meaning garden).

While English 'cow' is not related to Spanish 'vaca/vaquero' (as it comes from Germanic roots), the English word 'vaccine' is actually related! 'Vaccine' comes from the same Latin word 'vacca' (cow) because the first vaccination was developed from cowpox virus. The English word 'buckaroo' is also related, as it's actually a borrowed and anglicized version of Spanish 'vaquero'!