An old name for the 'down regions' of an old lady.
The use of the word 'slurp' comes from a Shakespearian reference when King Aurthur was said to 'slurp uponst thee that runs freely and with froth from the cunny of thy mother's mother', aparently referring to the frothy nature of his grandmother's lovejuice.
The term bucket is not confirmed, but is widely accepted to be a reference to the 'openning'.
Wakefield was pissed because Alice was passing round pictures of his Granny's Slurpbucket'. He's never been the same since.