The moon has powerful effects on the earth
Gravity effects the fluids on earth as manifested in tides.
Human female reproductive cycles are often related to the effects of gravity, much like tides. The human female reproductive cycle mimics lunation and in many cultures the moon is a female deity.
Shape-shifting is induced by the effects of a full moon bringing werewolves out of seemingly normal people.
The indigenous people of North America named each full moon throughout the year.