Found this on pompey web.......
Origins of the term "Scummer"
An interesting story came the posse's way a few weeks back about the true origin of the term scummer or scum. Apparently, just before the first world war, a dispute broke out between a local fishing company and it's employees. We don't know the name of the company, but we do know that it had two branches, one in Portsmouth and the other in S***hampton. The dispute, over wages, escalated and eventually the union called a strike, which was solid among both the Portsmouth company union men and the S***hampton company union men. Nothing was resolved, and after some weeks the S***hampton company men broke the strike and went back to work, thus ensuring the collapse of the dispute without any gain for the employee's of either company. Not suprisingly, the Portsmouth company were incensed at the actions of thier fellow workers, and apparently one wag noticed that the first letters of the S***hampton Company Union Men spelt SCUM. Hence the name Scum or Scummer as a term of abuse for anyone from S***hampton was first coined. Taken form the hard copy of the April/May 1996 issue of Frattonise
and there you have it!