The Spanish word 'vejiga' (meaning 'bladder') comes from the Vulgar Latin word 'vessica', which in turn derives from Classical Latin 'vesica', also meaning 'bladder'. The evolution from Latin to Spanish shows typical sound changes: the Latin 's' became a 'j' sound in Spanish (represented by the letter 'j'), and the double 's' in Vulgar Latin 'vessica' was simplified to a single 'j' in Spanish.

While 'vejiga' itself is a relatively common anatomical term in Spanish, there aren't many simpler or more common Spanish words that are directly derived from the same Latin root. However, you might encounter related medical terms like 'vesical' (relating to the bladder) which preserves the original Latin form more closely.

English speakers might recognize the connection to scientific or medical terms like 'vesical' (relating to the bladder) and 'vesicle' (a small fluid-filled sac or bubble), which come from the same Latin root 'vesica'. The word 'blister' in English is sometimes referred to as a 'vesicle' in medical terminology.