Thunderbird is one of the four houses of Ilvermorny School of Witchcraft and Wizardry. The name was chosen by Chadwick Steward. Thunderbird house stands for the soul of the wizard and is the house for adventurers.
The Thunderbird is a magical creature of North America. It figures in the mythology and legends of peoples from all over the continent, but the Algonquian legends would be most apropos for the location of Ilvermorny. The name comes from the fact that the bird throws lightning bolts and creates thunder by flapping its wings.
From the Web
Thunderbird on Wikipedia