The Spanish word 'obra' meaning 'work' comes from the Latin word 'opera', which meant 'work' or 'labor'. 'Opera' itself developed from the Latin word 'opus', also meaning 'work'. The evolution from Latin 'opera' to Spanish 'obra' shows a common sound change where the 'p' softened to 'b' between vowels, a frequent phenomenon in the development from Latin to Spanish.

Several common Spanish words are related to 'obra', including 'obrero' (worker), 'obrar' (to work, to act), and 'maniobra' (maneuver). All these words share the same Latin root and maintain connections to the concept of work or labor.

English speakers might recognize this etymology in words like 'opera' (a musical work), 'operate' (to work or function), and 'opus' (an artistic work). These English words come from the same Latin roots as Spanish 'obra'. While 'opera' in English has specialized to mean a specific type of musical performance, it originally simply meant 'work' in Latin, just like Spanish 'obra'.