Dag is an Australian and New Zealand slang term, also daggy (adjective) and dagging (verb, to behave in a daggy way). In Australia, it is often used as an affectionate insult for someone who is, or is perceived to be, unfashionable, lacking self-consciousness about their appearance and/or with poor social skills yet affable and amusing. It is also used to describe an amusing, quirky and likeable person (as in, "He's a bit of a dag") and is non-pejorative. The term was more widely used in the 70s due to the popular New Zealand comedy of Fred Dagg (John Clarke).
Differentiated from bogans, whose accents are presumed to indicate working class or uneducated origins, dag refers to being unfashionable, eccentric and fool-like and hence has no necessary ties with social class or educational background.
The literal meaning is a dung-caked lock of wool around the hindquarters of a sheep – an abbreviation of "daglock".
Originally a word meaning the dried faeces left dangling from the wool on a sheep's rear end, the word dag is more commonly used in colloquial Australian English to refer to someone's unfashionable, often eccentric or idiosyncratic style or demeanor together with poor social skills and amusing manner.
This colloquial use of the term "dag" was first recorded in the Anzac Songbook in 1916 but has been popular since the 1970s. It has also been used interchangeably with the term "wag" as in "what a wag", which refers to the amusing aspect inherent in 'dag' but without referring to fashion or style.
This use of "dag" comes closest in meaning to the UK slang term "pillock" (meaning fool) but "dag" is differentiated from terms like , nerd or geek by virtue of having no particular association with a drive for intellectual pursuits or interest in technology and no particular tendency towards being a loner. It is also used differently in that it can be an affectionate term as much as, or even more than, an insult. However, one can simultaneously fit the archetype for a dag and a geek, dork or nerd.
Whilst "bogan" refers to being unfashionable in the slovenly sense, it is distinguished from "dag" in that the term "bogan" has no necessary links with being eccentric, idiosyncratic or amusing. Similarly, the more antisocial behaviours associated with bogans are usually not found amusing and are more associated with terms like yobbo.