I have also found evidence it goes back even further.

In the Old Testament, under the laws provided to the newly liberated Hebrews, Exodus 22:2 states, “If a thief is caught while breaking in and is struck so that he dies, there will be no bloodguiltiness on his account” (New American Standard Bible)

The modern law basically says that your place of residence is one in which you should be able to protect yourself from illegal trespassing and attack. Some states have recenctly updated the legislation and now also gives this kind of protection to you while you are in your vehicle as well as your place of employment.

This law gives you the legal right to use deadly force to defend your Castle. In a legal context, therefore, use of deadly force which actually results in death may be defended as justifiable homicide under the Castle Doctrine.

Each state is responsible for it's own castle law legislation so it is very important for homeowners everywhere to understand the laws they are governed by. For instance, some states have a stand your ground aspect while others employ a duty to retreat clause and they have big impacts on how you have to handle yourself in your own home to make sure you are fully protected.