The Spanish verb 'bañar' (meaning 'to bathe') comes directly from the Latin word 'balneare', which also meant 'to bathe'. Over time, as Latin evolved into Spanish, the 'ln' sound combination in 'balneare' transformed into the Spanish 'ñ' sound, a common phonetic development in Spanish. This change made the word easier to pronounce while maintaining its original meaning of bathing or washing.

Some common related Spanish words include 'baño' (bath/bathroom), 'bañera' (bathtub), and 'bañista' (bather). All these words share the same Latin root and form a family of words related to bathing and washing.

While English 'bath' comes from a different Germanic root, we do have some related words borrowed from the same Latin source, such as 'balneology' (the study of therapeutic bathing and medicinal springs) and 'balneotherapy' (treatment of disease by baths). However, these are specialized medical terms and not commonly used in everyday English.