How Did Shaking the Head Come to Mean “No”?
The origin of this method of indicating “No” is found in the result of the mother’s efforts in the animal kingdom of trying to feed her young. A mother animal would be trying to get her young to accept the food she brought them and tried to put it in their mouths. Perhaps, however, the young animal had had sufficient food or did not fancy the kind of food offered. The natural thing to do under the circumstances would be to close the mouth tight and shake the head from side to side to prevent the mother from forcing the food into the mouth. Thus we get the closed lips and the shaking the head from side to side to mean “No.” In other words, that kind of a way of saying “No” came from an effort to say “I don’t want any.”