To settle means to come to order or rest, much as snow settles on the ground or dust settles on the dining room table.
Settle has a number of meanings. After moving several times, you'll wish your parents would settle in one place for the rest of your school years. Have you ever heard your house creaking or groaning? That's the house settling. When adults tell children to calm down, they'll often say, "Settle down kids!" And as a legal term, you settle a lawsuit when the accuser and the accused come to an agreement without going to court.