Repeated thinking about the same thing is called rumination. It derives from the method of digestion and absorption of some herbivores such as cattle. This is the same in both Japanese and English. When there is an event that cannot be digested, keep a certain distance from it. Let time pass by.It's like marinate, and like cooking. It is a work created in the image of a weight when making Tsukemono(fermented food) and digestive organ.The stone placed on the grave may also be this weight.