To be dan is to be angry to an extent where
head explosion can be readily achieved. originating in the Australian cities of Albury/Woodonga, after a local celebrity
got so angry at a practical
joke, that his
head swelled up and became so red that it was close to exploding, and then sent abusive messages to many of the people of Albury/woodonga abusing them and threatening them. after the indecent "dan" became a popular phrase used to emphasize one's anger/frustration.