May also come
from the Tasmanian sheepfarming term 'to dag the hogget', i.e. to remove
of a sheep by biting open the scrotum and sucking
them out of the sack. After a day of this gruelling work one would be left covered in sheep's blood and faeces, leaving the person 'daggy'. See Errol Flynn's autobiography 'My Wicked Wicked
Ways' for a graphic description of this practice.