A mill pond is a body of water used as a reservoir for a water-powered mill.

Why is it called a mill pond?

Mill ponds were often created through the construction of a mill dam or weir (and mill stream) across a waterway. ... The term mill pond is often used colloquially and in literature to refer to a very flat body of water. Witnesses of the loss of RMS Titanic reported that the sea was "like a mill pond".

Is the saying mill pond or milk pond?

A mill pond is formed by damming a stream to produce sufficient head of water to operate a watermill. Mill ponds are invariably described as smooth or calm. Milk too is smooth, and could be described as calming as well as nutritious.