Posted by Bruce Kahl on April 04, 2000
In Reply to: As Dead As A Door Nail posted by James Briggs on April 04, 2000
One theory holds that the "doornail" in question was not a nail as we know nails today, but rather a broad, flat plate mounted on the outside of the door to serve as a striking plate for the door knocker. Such a "nail" would be "dead" because it would be fixed tightly to the wood of the door and thus would not ring when struck as metal normally does, but rather give a dull "thump." This theory is both labored and unlikely.
Another theory is expounded by etymologist Robert Claiborne, who noted that until the nineteenth century metal nails were both expensive and rarely used with wooden pegs being the norm. Metal nails were used in the construction of doors, however, usually driven clear through the door and then bent over on the other side, rendering them immovable (and immune to theft). Such nails were "dead" in the lingo of carpentry because they could never be removed and reused. "Dead as a doornail" is thus not just a very old saying, but a very old pun as well.