The Spanish word 'tétano' (meaning tetanus) comes from the Latin word 'tetanus', which in turn was borrowed from the Ancient Greek 'τέτανος' (tetanos). The Greek word originally meant 'rigid' or 'tense', which perfectly describes the main symptom of the disease - muscle rigidity and tension. This direct connection between the original meaning and the disease's symptoms helps explain why this term was chosen to name the condition.

While 'tétano' itself is a relatively straightforward medical term in Spanish, there aren't many simpler or more common Spanish words that share its Greek root. This is because the word was borrowed specifically as a medical term and didn't generate a broader word family in Spanish.

English speakers will readily recognize the cognate 'tetanus', which is identical to the Latin word and very similar to the Spanish 'tétano'. The only difference is the final '-us' versus '-o' ending, which is a common pattern when Latin words were adapted into Spanish. Both languages preserved the medical meaning of the term. The English adjective 'tetanic', meaning 'of or relating to tetanus' or 'characterized by muscular spasms', is also derived from the same root.