Two professions where nicknames become working names: rap music and insurance.
So, like Belcalis Almanzar works as Cardi B and Christopher Wallace got famous as The Notorious BIG (RIP, btw), people widely refer to American International Group as AIG and casually refer to Marsh & McLennan as M & M. (In rap, Eminem's real name is Marshall Mathers. Do we smell sponsorship deal? Don't you think Eminem's M & M track would be bangin'?)
These are the alphabet brokers in the insurance business - companies more famous as their initials than they are for their full names. Given how boring the official names for insurance brokers tend to be, you can see why this has become popular. More broadly, the term "alphabet brokers" is slang for large U.S. insurance brokers generally.
