The Spanish word 'oso' (meaning 'bear') comes from the Latin word 'ursus' (also meaning 'bear'), specifically from its accusative form 'ursum'. During the evolution from Latin to Spanish, the initial 'u' sound changed to 'o', and the 'rs' consonant cluster simplified to 's', giving us the modern Spanish word 'oso'.

The word 'oso' is relatively simple and common in Spanish, being one of the basic animal vocabulary words. It doesn't have many simpler related Spanish words, as it is already a fundamental term.

While English 'bear' is not related to 'oso', there are several English words that come from the same Latin root 'ursus'. These include 'ursine' (meaning 'bear-like' or 'relating to bears'), and the name of the constellation 'Ursa Major' (the Great Bear). The chemical element 'uranium' was also named after the planet Uranus, which in turn was named using this Latin word for bear.