An Australian slang term.
A dag is technically the matted wool on a sheeps tail, but in typical useage throughout
Australia, it refers to people who
don't have a neat, tidy or cultured appearance. It can also refer to a
person who tends to be quite informal.
It is not necessarily a derogatory term in modern useage.
It can also refer to a Person who is a bit zany in antics in a loveable way