dead as a doornail

(as) dead as a doornail

1. Definitively dead. (Doornails were hammered in a such a way that they could not be reused.) I poked that squirrel with a stick and, yeah, it's as dead as a doornail.
2. Totally defunct. That idea from last week's meeting is dead as a doornail now that the CEO has vetoed it.
See also: dead, doornail
Farlex Dictionary of Idioms.

dead as a doornail

Also, dead as a dodo or herring . Totally or assuredly dead; also finished. For example, The cop announced that the body in the dumpster was dead as a doornail, or The radicalism she professed in her adolescence is now dead as a dodo, or The Equal Rights Amendment appears to be dead as a herring. The first, oldest, and most common of these similes, all of which can be applied literally to persons or, more often today, to issues, involves doornail, dating from about 1350. Its meaning is disputed but most likely it referred to the costly metal nails hammered into the outer doors of the wealthy (most people used the much cheaper wooden pegs), which were clinched on the inside of the door and therefore were "dead," that is, could not be used again. Dead as a herring dates from the 16th century and no doubt alludes to the bad smell this dead fish gives off, making its death quite obvious. Dead as a dodo, referring to the extinct bird, dates from the early 1900s.
See also: dead, doornail
The American Heritage® Dictionary of Idioms by Christine Ammer.

dead as a doornail

1. If a person or animal is as dead as a doornail, they are completely dead. From the start of the movie it is clear that she will be as dead as a doornail by the time the credits roll.
2. If something or someone is as dead as a doornail, they are no longer active or popular. My $2,500 computer was dead as a doornail. Nobody will hire him now. He's finished. Dead as a doornail. Note: It is not certain what `doornail' actually refers to. In medieval times, it may have been the plate or knob on a door which was hit by the knocker. It was thought that anything that was struck so often must have been dead. Alternatively, doornails may have been the thick nails which were set into outer doors. It is not clear why these nails should be described as `dead'.
See also: dead, doornail
Collins COBUILD Idioms Dictionary, 3rd ed.

dead as a doornail (or as mutton)

completely dead.
A doornail was one of the large iron studs formerly often used on doors for ornamentation or for added strength; the word occurred in various alliterative phrases (e.g. deaf as a doornail and dour as a doornail ) but dead as a doornail is now the only one in common use.
See also: dead, doornail
Farlex Partner Idioms Dictionary

(as) ˌdead as a ˈdoornail

(informal) completely dead
See also: dead, doornail
Farlex Partner Idioms Dictionary

dead as a doornail

Undoubtedly dead.
See also: dead, doornail
American Heritage® Dictionary of the English Language, Fifth Edition.

dead as a doornail

Dead, unresponsive, defunct. This simile dates from the fourteenth century and the source of it has been lost. A doornail was either a heavy-headed nail for studding an outer door or the knob on which a door knocker strikes. One plausible explanation for the analogy to death is that it alluded to costly metal nails (rather than cheap wooden pegs), which were clinched and hence “dead” (could not be re-used). The expression was used in a fourteenth-century poem of unknown authorship, William of Palerne, and was still current when Dickens wrote A Christmas Carol (1843). There have been numerous similar proverbial comparisons—dead as a mackerel, dead as mutton, dead as a herring, dead as a stone—but this one, with its alliterative lilt, has survived longest.
See also: dead, doornail
The Dictionary of Clichés by Christine Ammer
See also:
  • (as) dead as a doornail
  • as dead as a doornail
  • doornail
  • herring
  • (as) dead as a herring
  • (as) dead as mutton
  • mutton
  • dead as mutton
  • be dead in the water
  • dead in the water
References in periodicals archive
Alliteration is found in many common phrases, such as "pretty as a picture" and "dead as a doornail." In its simplest form, it reinforces one or two consonantal sounds, as in this line from William Shakespeare's Sonnet XII: