'Brass neck'.
It is a compilation by one guy. He doesn't even have 'brassic' in there. Does that mean Londoners do not use that term?
In addition, language constantly changes, slang comes and goes. The cockney guys I knew who used 'Kimo sabe' to mean, 'Do you speak English?'
The whole aim of Cockney villain slang is to speak in a code that the police wouldn't understand, and they even invented a backslang for this purpose.
(No, I am not cockney and I never followed the Lone Ranger, thanks for asking.)