The code names were revealed at an event when one of Harry's aides told a worker that someone was trying to contact him.
But, failing to recognise the name on the assistant's mobile, the confused worker asked why the person on the line wanted to speak with him.
The source added: "Imagine the surprise he got when he heard Harry's voice on the other end of the line."
However, while members of the royal family are known by their secret code names to bodyguards and aides, when in private with their loved ones, they refer to each other by at least one nickname.
The Queen is known as "Gary" courtesy of Prince William who, as a youngster, struggled to pronounce "granny" and would call her Gary instead.
And Prince William's son, her great-grandson Prince George, has reportedly nicknamed the monarch "Gan-Gan".
Prince Charles is said to call Meghan Markle 'Tungsten' after the metal, because of her "tough and unbending" nature.
Kate Middleton and Prince William use terms of endearment by referring to each other as "darling" and "babe", while Meghan was recently overheard calling Prince Harry "my love" while watching the hit West End musical Hamilton with him.