A Ginger Newt is a type of sweet in the Wizarding world, taking the form of a newt-shaped biscuit. Professor Minerva McGonagall, during her days as professor of Transfiguration at Hogwarts School of Witchcraft and Wizardry, was known to keep these in a tin in her office. When McGonagall scolds Harry Potter and George Weasley for their fight with Malfoy on the Quidditch pitch, she slams her fist on her desk so hard that the tin of Ginger Newts falls on the floor and spills everywhere. 
Behind the scenes
- Ginger Newts appear to be a parody of real life British biscuits, Ginger Nuts.