The stew Andy refers to was called 'lobscouse'. It was a mixture of vegetables and biscuit and commonly served to seamen in past times. Presumably, it is that sea-connection that caused it to attach itself to Liverpool and Liverpudlians.
"Lobscouse" is similar to a Norwegian word, "Lapskaus" and it's been suggested that fishermen from Norway introduced the dish to Liverpool. It's not unusual for people to be nicknamed after food associated with them; compare "Kraut" for German, "Limey" for Englishman and "Spud", I suppose, for Irishmen!
Thjere is scouse which is a meat stew with vegetables and 'blind scouse' which is meat stew without the meat. Blind scouse was often eaten towards the end of the week when funds were low. I can't believe there hasn't been a deluge of Scousers offering an answer to this one, they're not usually this quiet.