In ancient myths and legends in China, there are Chang 'e and Jade Rabbit on the moon. Later, people used to call the moon Chang 'e or Jade Rabbit.

The moon is a satellite of the earth where we live. It goes around the earth, once a month. Whenever the first month of the lunar calendar begins, you can see the crescent moon at night, which can be said to be "very thin". And every time near the fifteenth day of the month, the moon will gradually "thicken" until it becomes round.

The "thin" and "thick" in this question should refer to the moon. Therefore, the answer to this question is the zodiac rabbit.