How does Tom's puppy get its name in the story, A Member of the Family?

When Dr. Lockwood comes in from work and meets the dog, he laughs at it and immediately starts calling it "Precious," much to the consternation of Mrs. Lockwood, who has always wanted to name a dog "Prince." In spite of all her efforts, the little ball of fluff, which grows to an enormous one hundred twenty-five pound powerhouse, is known to one and all as Precious.