The Cockney term for Rabbit is a person who likes to talk alot, and not stop talking, bit like my youngest daughter (6) all day every day Rabbit Rabbit... She just wont shut up Hope that helps
A lot of cockney slang used two words like Titfer-Tat = hat
Over time one of the words gets dropped away so then you get Titfer = hat
and so it is for rabbit = talk since the original was rabbit and pork = talk