"To assuage Tereza's sufferings, [Tomas] married her […] and gave her a puppy" (1.11.1). The female puppy was half Saint Bernard and half German shepherd.
Tomas wants to give the puppy a name that will indicate it belongs to Tereza, not to both of them. Tereza chooses to call it Karenin (a male character from Tolstoy's Anna Karenina) even though the puppy is a girl.
The puppy quickly falls in love with Tereza. Tomas is pleased, as he got the dog to share some of the responsibility to love her.
Yet, in the long run, Tomas would still fail to make Tereza happy. He realizes this years later, in August of 1968, ten days after his country is occupied by Russia, when the director of a hospital in Zurich kept offering Tomas a job.