From the 1811 Dictionary of the Vulgar Tongue. Also called 'Cat Lap' or 'Chatter Broth,' it refers simply to tea, one of the greatest beverages ever. Named for the amount of conversation and gossip often shared while having tea during the Georgian/Regency & Victorian eras. At the time, it was intended to refer to gossip shared by women in particular (but let's be honest. It definitely wasn't just women sipping tea & spilling secrets behind closed parlor doors).

1811 Dictionary of the Vulgar Tongue, by Francis Grose
Additional information from InfoPlease and the Dictionary of Phrase and Fable, E. Cobham Brewer, 1894