the girl next door

The girl next door is a cliche which refers to anyone who is ordinary, normal, not rich and famous, or nobody in particular that is exciting to someone else. Rather than being a literal term for a girl who lives next door to you, this term is used for any girl (or boy in boy next door) that seems very ordinary, such as the person living next door to you and not in some elaborate mansion or that has a lot of money and power.