Wow, i had no idea it came from the term Scallywag. My mum used to call them scallywags, and we laughed at her.
Me and my friends came up with the theory that when many 'Scallies' congregate in one place such as a busstop or a train station, this is called a 'Wag' which is where Scallies go to breed, and spawn more Scallies. Hence why there is always at least one Scallie female.
The whole event is called a Scallywag.
I will agree you look a tiny bit chavish in the photo, aside from the cheerful dancing. Not that i am calling you chavs, or indeed scallies, but glancing at the photo without scrutiny, there is essence of Chav.