Where did the term 'dead as a doornail' or 'dead as a doormouse' come from?

Dead as a doornail is an expression most of us learned first in Dickens's "A Christmas Carol". Actually, it's much older than that, having appeared in the fourteenth-century "Vision of Piers Plowman" and in Shakespeare's "Henry IV".

The dictionary defines a doornail as 'a large-headed nail, easily clinched, for nailing doors, through the battens.' Now the 'clinching' makes the nail 'dead'. It cannot be easily withdrawn. 'Dead-nailing' is a term most any carpenter is familiar with. It is a technique frequently used in constructing doors for log cabins, construction shanties and the like - and it antedates the ready availability of screws and more sophisticated fastening devices.

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