It is not widely known but Rudy had a codename amongst his inside crew. 'Crew' was a term my father rather liked to describe Rudy's staff (more mafia connotations). Early on it became necessary to refer to Rudy in conversation between ourselves without anyone around knowing of whom we were speaking. It might be in a restaurant, the street - basically any crowded situation. "Rudy needs you to do this" or "Rudy wants you at Gracie at 9PM."
In addition, back then, we were generally of the belief that cell phones were not secure. I don't mean in the way that the NSA or the Russians can listen in. I mean back in the early 90's there was a widely-held belief that cell phones were much like cordless phones in their level of security. I do not know if any of those recorded Charles & Diana calls to their lovers were over cell phones, but I recall one Giuliani aide referring to them in conjunction with the need to be careful when speaking on our cells.
So Ray Harding came up with 'Ralph'. Whenever security was an issue Rudy was always referred to as Ralph. Back then, now too for that matter, most people did not know a Rudy in their daily life. The only Rudy most people 'knew' or ever heard about was the mayor. So if you mentioned his name and especially in the contexts we were, it was bound to be understood as 'that' Rudy. You can blather on for hours about Mike and no one will take any notice of what you're saying. But start talking about Rudy and ears perk up. Interestingly, much like their mayoralties.