Last Name, Surname
Your clan is where you get your name. But not your given name, your family name. That's why people have names that mean "in a rice paddy" and "near the ferry crossing." The location of your clan determined your surname! Hope your ancestors didn't live on "Poo Lake" or something.
Don't worry, I'll tell you where your family name came from. Your family used to herd sheep (し). You read that right, your family was of the sheep clan because you took care of sheep all day.