The Spanish word 'plumón' (meaning 'down feather') comes from the Latin word 'pluma' meaning 'feather'. It entered Spanish as 'pluma' and then combined with the Spanish augmentative suffix '-ón' to form 'plumón'. The augmentative suffix in this case doesn't make the feather bigger, but rather indicates a softer, fluffier type of feather - specifically the soft, insulating down feathers found under the tougher exterior feathers of birds.

The most obvious related Spanish word is 'pluma', which simply means 'feather' or 'pen'. The connection between feathers and pens comes from the historical use of feather quills as writing instruments. While 'pluma' refers to any feather or a pen, 'plumón' specifically refers to the soft down feathers.

While English 'plume' comes from the same Latin root 'pluma', it has taken on a slightly different meaning, typically referring to a large, showy feather or a decorative bunch of feathers. We can also see this root in words like 'plumage' (a bird's feathers collectively) and 'plumed' (decorated with feathers). The connection between Spanish 'plumón' and these English words helps remind us that they all relate to feathers in some way.