When Christopher Columbus and his crew first arrived in the Americas, they noticed that many of the native people chewed the dried leaves of a plant that was unknown in Europe. They also noted that some people placed burning leaves in a cylinder, called a tabaco, and inhaled the sweet-smelling smoke by sucking on the opposite end of the cylinder.
A few sailors experimented with the process, found they liked the taste, and soon other sailors followed their example. The Europeans quickly adopted the “chewing” and “smoking” habit. However, since most boats were made of wood at that time, captains forbade smoking the leaves on board. If the ship’s store ran out of tobacco leaves on a voyage, many sailors turned to chewing leather strips, pieces of fat, or rags as a substitute
. Because much of the chewing took place when the sailors had free time, the expression “chew the fat” was coined to refer to sailors sitting around telling stories. In time, to “chew the fat” came to mean sitting and chatting about nothing of great importance.
It is also been thought that this phrase is related to cloth, when ladies would work in “sewing circles” or that women may have gossiped while quilting.