chew the fat
informal

- to talk with someone in an informal and friendly way

The Cambridge English Dictionary

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ORIGIN

Although some sources attribute the phrase "chew the fat" to sailors, who during a period of resting and conversing, or while working together, would chew on salt-hardened fat, there are no reliable historical recordings of this practice. There is even a suggestion the phrase derives from a practice by North American Indians or Inuit of chewing animal hides during their spare time, and even of British farmers chewing on smoked pork, but again, there remains to be no evidence supporting these claims, and this would require accepting a great deal of uncertainty in connecting the phrase from nautical origins to its modern metaphorical use.

There are also claims the phrase is synonymous with the action of chewing on fat, or simply an allusion to the movement of the mouth during chewing. Noting that fried fat is appealing in taste, it was regarded as a treat that someone could chew on for as long as possible to gain the most out of it.

According to the Oxford English Dictionary, "Chew the fat" first appeared in 1885 in a book by J. Brunlees Patterson called Life in the Ranks of the British Army in India. He implied it was a kind of general grumbling and bending of the ears of junior officers to stave off boredom, a typical part of army life.

Patterson also uses "chew the rag" in the same sentence he used "chew the fat", but it is not the oldest occurrence. Prior to the adoption of metallic cartridges, most ammunition was composed of powder and a ball wrapped in paper or cloth soaked in animal fat, which was bitten open during musket drill. Soldiers were known to chew on these ends to pass the time and reduce nerves, and in some cases to stave off cravings for chewing tobacco.

Though long-since replaced by 1885, the idea of biting or chewing on fat-soaked rag ends may well have entered military parlance in this fashion prior to Patterson's recording.

Sources: Wikipedia, The American Heritage dictionary of idioms, Wilton, David (2004, Oxford University Press)

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SYNONYMS

chat, talk, converse, speak to each other, discuss things, have a talk, have a conversation

informal: have a tête-à-tête, a chat, a chinwag; to jaw, rap, yak, yap, natter, rabbit, shoot the breeze

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PRACTICE OWAD IN A CONVERSATION TODAY
Say something like:


“We were in the bar, chewing the fat, and telling stories about good old days."