Shylock says he will not give any particular reason except that it is his fancy and whim. He gives the example that if his house is infested with rats it is fancy to spend ten thousand ducats to have them poisoned. Further, he says that there are some people who cannot tolerate the sight of an open-mouthed roasted pig, others the sight of a cat and some get angry to hear the scream of the bagpipe. It is just a matter of personal taste. What we like or dislike is determined by our whim or mood.