In the 1800s and 1900s, most inhabitants of the city wouldn't have been able to claim ancestry here, the melting port of the growing port, influx of Irish, Scots and Lancastrians meant most families were fairly 'new' to the area. The 'Dickie Sam' was therefore the character of a Liverpudlian (or Liverpolitan as it would more commonly have been known), rather than birthright.
There are several possibly attributions, and as is often the way, the most common is the most unlikely. Tune in tomorrow to find out about Dickie...