Thought to be a hybrid between 'prat' and 'fanny', two quite inoffensive words which, when blended, create an equally inoffensive word.
Can be used to dilute harsher rude words.
Is often met with laughter.
In the porn industry, is an equivalent of a male "granny" : a male actor of ripe age performing sexual acts or intercourse, often with partners that are much younger.
The term comes from a combination of the "pa" part of "grandpa", and the word "granny", and can be a replacement term for "gramps".