the.com/doormat

means A flat mat placed at a doorway for wiping shoes — and, figuratively, a person who lets others walk all over them without protest.

from A plain compound of "door" and "mat," both old English household words: "door" traces back to Old English "duru"/"dor" (with cousins across the Germanic languages), and "mat" comes from Old English "meatte," itself borrowed early from Late Latin "matta," a mat of woven rushes. So the literal object is centuries old; the figurative sense — a person treated as something to be trodden on — is a much later metaphor, the unsurprising leap from a thing you wipe your feet on to a person who lets you.