Definition & Meaning of "[make] {oneself} at home"

What is the origin of the idiom "make oneself at home" and when to use it?

The phrase originated in the 19th century and was likely used in both Britain and the United States. The phrase suggests that a guest should feel comfortable and relaxed, as if they were in their own home. It is often used as a polite invitation for a guest to feel free to help themselves to food and drink, or to make any necessary adjustments to their surroundings. The phrase is also used in a broader sense to indicate a general feeling of welcome and hospitality, and can be used in both formal and informal settings. Overall, the phrase "make oneself at home" has come to represent a warm and welcoming attitude towards guests, and is an important part of many cultures around the world.