The Cockney lingo uses quite a few names of people, most of them are genuine names, some a little harder to fathom. A lot of it stems from market traders, certainly in the East End of London there are and always have been plenty of street traders. If they have their own language then it's easier for them to talk between themselves without the customers knowing too much. This is why a lot of Cockney incorporates lots of cultures and languages, from Yiddish to West Indian and all ports in between.
That was a little digression to get to today's word which is rhyming slang for 'punter', itself a slang word.
Whilst I can't find any definitive answer to where the word punter comes from, as 'punters' tend to always be paying customers I assume it derives from the word 'punt' which was an old Irish pound. 'Punters' seem to have origins in horseracing and to have got into common usage from there.
So to use this in a sentence:
"I only sell online these days, haven't spoken to a norman hunter in yonks" which translates to "mostly I sell on that internet thing, it has been a terribly long time since I have talked to a customer".