this seemingly random term comes from an Arrested Development meme:

Michael opens the refrigerator and sees a paper bag with "DEAD DOVE Do Not Eat" written on it. He opens the bag anyway and, there is, in fact, a dead dove inside. He says to himself, "I don't know what I expected."

• this tag was first proposed in 2015 as a fanwork metatag.
• it has been referred to as ‘a generic darkfic warning (…) a way to tell readers that, seriously, this fic contains something unpleasant – you have been warned. If you choose to ignore that warning and open the fic, then get upset by the unpleasant content, well, we don’t know what you expected.’ (whatisthehydratrashparty 2016)
  • i.e. a fanwork tagged “suicide” followed by “dead dove: do not eat” will contain a scene with a suicide. if you continue reading, you do so having been warned.
• the meaning has shifted a little to something more like ‘this fanwork contains morally reprehensible themes’
  • people used "dead dove" to just refer to all of the content that usually needs to be thoroughly warned for, and hence began to associate it with such themes
  • ‘dead dove’ is now sometimes used as a vague tag on a work that doesn’t include any actual trigger or content warnings, defeating the original purpose of it
  • for the purposes of this Notion you should consider it more like an ‘exactly what it says on the tin’ tag.