a.k.a. dagtag, dag tag
An overly elaborate sig quote. For example, if a user has "tagged on" twenty lines or more after the body of an e-mail message below their name (and if there is a typo, or more than one quote, or some kind of bogus ASCII art), it's known as a dag-tag.
It refers to "a dag" (which, as any good Aussie will tell you, is what gets stuck to the anus of a sheep after it's dropped its stool (Americans call those dingleberries)! So then, a dag-tag is the equivalent within an email message - a piece of sh*t that got stuck there but shouldn't have ;-)
NetLingo Classification: Online Jargon