James Potter calls Snape this when they were at Hogwarts themselves.
Dudley is also known as Big D
And before you complain in the comments, I purposely left out Tom Riddle in the data. He was only a figure of terror as Lord Voldemort. Also, Voldemort is known as You-Know-Who.
I put Petunia Evans in the data instead of Petunia Dursley because Harry's mother, Lily, called her Tuney when they were not married. Harry learns this in 'The Prince's Tale' the fourth to last chapter of the Deathly Hallows, not counting the epilogue.
According to Viktor Krum, Hermione is also Herm-own-ninny