1)Ticklish sub-region of the taint.
Once only thought of in theory - the fancy is the newly discovered spot located at the part of the perineum closest to the buttocks and the entrance of the ass crack. Often tickled by a wandering moustache or the delicate touch of a lovers forefinger - hence the term "tickling ones fancy".
Dr Boudreaux, in the midst of experiment number 142 in his salad tossing research, heard a sudden yelp of surprise from his female subject above - and so the elusive fancy was found. This was therefore the first documented account of fancy-tickling.