Green’s Dictionary of Slang

Johnny Walker n.¹

[rhy. sl. = talker; ult. Johnnie Walker, a brand of whisky]

1. a talker, a garrulous person.

1992		R. Puxley Cockney Rabbit.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.

2. an informer.

1992