Why are medical residents called "residents" anyway?
First of all, for those who are unclear about the terminology, a "resident" is the term applied to a doctor (either an M.D. or D.O) who has graduated from medical school and is continuing in clinical training in a certain specialty (e.g., internal medicine, pediatrics, OB/GYN, psychiatry, etc.).
In fact, the term "resident" was coined because in fact many doctors-in-training would gain their clinical experience in hospitals. In order to be there when the patients were needed, the doctors would actually live in the hospitals that employed them. For their services, the residents would have their room, board and laundry services paid along with a minimal wage.
Today, most residents only stay in the hospital if they are on call. And that is usually every 4 or 5 nights depending on their rotation. (Although my wife would argue that I live in the hospital with the amount of time I spend here.)