subside (v.)
1680s, of objects, "to sink to the bottom," from Latin subsidere "sit down, settle, sink, fall; remain; crouch down, squat," from sub "down" (see sub-) + sidere "to settle," related to sedere "to sit" (see sedentary). Of liquid surfaces, "to sink to a lower level, be reduced" from 1706. Related: Subsided; subsiding.