Snickerton was a Muggle tailor in fifteenth-century London, and the rival of Delfina Crimp.
Snickerton infiltrated Crimp’s shop and spied on her using magic at night, and then exposed her as a witch. Crimp escaped, and henceforth, any clothing Snickerton produced was shredded to ribbons overnight. He died insane, believing himself to be pursued by invisible giant scissors.
"Snicker" means to laugh at, a reference to Snickerton becoming a joke.