Even as a young Elvis impersonator, Bruno Mars wasn't going by his birth name of Peter Gene Hernandez. While he hadn't yet adopted the moniker of Mars, he was billed in Honeymoon in Vegas as Bruno Hernandez and was presented in all his Elvis interviews as little Bruno. So where did the name come from? His father gave him the nickname as a young child after the professional wrestler Bruno Sammartino.
He said in an interview with Rap-Up, "Bruno is after Bruno Sammartino, who was this big fat wrestler. I guess I was this chunky little baby, so my dad used to call me that as a nickname." He added, during an appearance on the The Graham Norton Show on BBC, "[Sammartino] was a stocky guy and I used to walk around like a little bulldog, my dad said, so he would always call me Bruno Sammartino."
In August 2017, Mars finally had the opportunity to meet his namesake, posting on Instagram, "I was nicknamed after this professional wrestler Bruno Sammartino. Tonight in Pittsburgh I had the honor of meeting him!" It was apparently a good time for the both of them — CBS Sports notes that Sammartino said of meeting Mars, "I hope he's like that in everyday life. He was the most humble, nicest guy. He couldn't have been more respectful."