The Spanish word 'buba' (meaning a small pus-filled swelling) traces back through an interesting medical history. It comes from the Spanish word 'bubón' (meaning a swollen lymph node), which itself derives from Medieval Latin 'bubo' (meaning swelling). The ultimate source is the Ancient Greek word 'βουβών' (boubon), which specifically referred to a swelling in the groin area. Over time, the meaning has become more general to refer to any small swelling containing pus, while retaining its medical context.

A closely related Spanish word is 'bubón', which refers specifically to a swollen lymph node or bubo. While 'buba' refers to any small pus-filled swelling, 'bubón' retained the more specific medical meaning closer to the original Greek term for groin swelling. These words are often encountered in medical contexts and historical descriptions of diseases like the bubonic plague.

English speakers might recognize this word's connection to 'bubo' and 'bubonic', as in 'bubonic plague' - the infamous Black Death that affected medieval Europe. These English terms share the same Greek ancestor as the Spanish 'buba'. While the English terms specifically refer to the characteristic swollen lymph nodes of the plague, the Spanish 'buba' has evolved to describe any small pus-filled swelling.