Scouse, the unique Liverpool accent, and, Scouser, the term for a Liverpudlian, are both derived from a traditional sailor’s stew.
Scouse was originally a poor man’s meal, made of beef, potatoes, onions, salt, and pepper. For sailors at sea, salt beef and crumbled hard tack (dried biscuits) were swapped in for the regular meat and potatoes. The origins of scouse, initially lobscouse, are hard to pin down, as versions have been consumed across northern Europe and Scandinavia for centuries, traveling from port to port with the sailors who consumed it. It’s remained a particularly popular dish in port towns, which is how it’s found a home in Liverpool.
Scouser as a reference to someone from Liverpool came into common use in the 1940s. It was originally a derogatory term that implied that the person was so poor that they could afford to eat decent food only once a week and, for the rest of it, ate leftovers boiled up with potatoes. But Liverpudlians took the insult in stride and turned it around into their own salutatory description.