What's the significance of the title of "The Rocking-Horse Winner"?

Without the rocking horse, young Paul would not be blessed
with the good luck that, according to his mother, has always avoided his father.
Although Paul has outgrown his childhood toy, he somehow determines that riding the
horse will provide him with the winners of the local horse races. He does not predict
the winners randomly or by himself; they come only while he secretly simulates the
actual races on the rocking horse, and he apparently always picks (or the wooden horse
whispers to him) the winner of the race. Critics claim that the horse also serves as a
symbolic sexual device, as Paul works himself up to a furvor while wildly riding the
wooden horse.