"Chew the Fat"
Chewing the fat means having a conversation with someone, or informal talk, or chat in a relaxed way. It also meant to grumble or complain. It was most popular in the 1800's with the British army. It slowly made its way to the United States. They think it originated by the army men being given tough meat to eat and they had to chew the fat of the meat. Chewing is like the action of speaking so that is how it got interpeted. The phrase is also known as chew the rag which means the same thing.
Examples: Let's chew the fat some time, and I had a great time chewing the fat with my old friend.