I say it all the time, I know what it means, but how did they come up with that phrase? Meaning that it is not alive, unequivocally deceased it can be figuratively or literally defunct – the phone line is deader than a door nail or that possum, you ran over, is as dead as a doornail.
Door nails were long used to strengthen the door. The person building or installing the door would hammer the nail all the way through the boards. On the other side, he would hammer the end flat, bending it so that the nail would strengthen the door in a process, called “clenching or clinching”. This rendered that nail unusable for any other purpose. It would be difficult to remove and even more difficult to use again elsewhere. The bent nail was referred to as “dead”. A 1948 study by the U.S. Forest Products Laboratory concluded that clinching can increase the holding power of a nail between 45 percent and 464 percent – depending on a variety of factors, including the species of wood and its moisture content.
There are automated clinching machines that shoot the nail through the wood into the back of a steel plate, waiting on the other side. The nail bends as it strikes the metal. My Dad just drove the nail through and then just hit it with the hammer on the other side, bending it into place. I use screws and avoid killing nails.
Marley was dead, to begin with. There is no doubt whatever about that. The register of his burial was signed by the clergyman, the clerk, the undertaker, and the chief mourner. Scrooge signed it. And Scrooge’s name was good upon change for anything he chose to put his hand to.Charles Dickens (from A Christmas Carol)
Old Marley was as dead as a door-nail.
Mind! I don’t mean to say that I know, of my own knowledge, what there is particularly dead about a door-nail. I might have been inclined, myself, to regard a coffin-nail as the deadest piece of ironmongery in the trade. But the wisdom of our ancestors is in the simile; and my unhallowed hands shall not disturb it, or the Country’s done for. You will therefore permit me to repeat, emphatically, that Marley was as dead as a door-nail.
This parrot is no more! It has ceased to be. It’s expired and gone to meet its maker. This is a late parrot. It’s a stiff. Bereft of life, it rests in peace. If you hadn’t nailed it to the perch it would be pushing up the daisies. It’s rung down the curtain and joined the choir invisible. This is an ex-parrot.Monty Python (Dead as a doornail parrot)
Brave thee! Aye by the best blood that ever was broached. And beard thee too. Look on me well: I have eat no meat these five days; yet, come thou and thy five men, and if I do not leave you all as dead as a doornail, I pray God I may never eat grass more.William Shakespeare (Henry IV Part 2)