The Spanish word 'tapón' (meaning 'stopper' or 'plug') comes to us through French 'tapon' (with the same meaning), which ultimately derives from the Frankish word '*tappo'. Frankish was a Germanic language spoken by the Franks, who conquered and ruled over what is now France during the Early Middle Ages. The asterisk in '*tappo' indicates that this is a reconstructed word form that linguists believe existed, though it wasn't directly recorded in surviving texts.

This word is related to the Spanish verb 'tapar' (to cover, to plug), and the noun 'tapa' (lid, cover). These words form a family of related terms all dealing with covering or stopping up something. While 'tapón' specifically refers to a stopper or plug, 'tapa' is more general and can refer to any kind of cover or lid.

While English 'tap' might seem related, it actually comes from a different Germanic root. However, English has borrowed the French word 'tampon', which comes from the same Frankish root as 'tapón'. Both words share the basic concept of something used to plug or stop up an opening, though 'tampon' has taken on more specific uses in English.