Why is Sunderlands nickname the black cats?

Answer 1

When Sunderland moved from Roker Park to the Stadium of Light, their old nickname such as the Rokerites, were not relevant

They asked supporters what they wanted their nickname to be.

Several suggestions were sent to the club and over 11,000 fans voted ' the black cats ' and this became their nickname.

Answer 2

The black cat appears on the coat of arms of the city of Sunderland, and has been adopted as such for the badge of the football team.