a variation of the
phrase chew the cud, meaning to think deeply and continuously about something; to reflect or mull over in one's
mind. The
phrase chew the cud was first seen in
use in the
late fourteenth century and referred to the practice of cows who, after
chewing and swallowing food, would bring it back up into their mouths again and
chew it up more (cud means the mouthful of food that is
chewed in this manner). Its figurative meaning came into
use around the end of the sixteenth century.