Chihuahua originate in Mexico. It was bred from precursor called the Techichi, which was a little dog that was kept as a pet by the Toltec Indians.
There were depictions of Techichi and Chihuahuas in Mesoamerica all the way through first millenium, the middle ages.
The Spaniards noted them when Cortez came to Mexico, he said that these little dogs were kept as pets and as food.
They were also used as living got watter bottles and what that means, when a person was sick and had a cold from a fever or something, they would stick a Chihuahua through the covers with them, because they were so small and the body warmth of the Chihuahua would warm the sick person up.
Why do the shiver all the time? One reason Chihuahuas shake is because they're cold. This is the smallest breed of dog and they have very, very low body fat.
They have hard time regulating their temperature and they get cold all the time. So, if you see a Chihuahua trembling, you definitely want to warm him or her up.
There you go, also please check the super cool collection of Chihuahua owners tee by CLICKING HERE or on the photo below.