Alan was christened Allan William Walsh at St Chad's Church of England in Cremorne on 5 May 1918. However it was not until it was necessary for Alan to present his birth certificate to the NSW Public Service Board when he began work 17 years later that he knew that his name had been registered Allan William Ernest Walsh. When he told his family at the dinner table that night, his mother's cool comment to his father was; "So you got your own way after all." It was Alan's first indication that his father had wanted his son named Ernest.
Although his registered name was spelled "Allan" he always spelt it "Alan" himself.
Well before the Second World war Alan enlisted as a gunner in the 1st Anti-Aircraft Battery in Mosman, NSW. The nick name "Gunner" was given to him by his sporting mates when he used to come to practice still in uniform. He was still known as "Gunner" 50 years later amongst his sporting friends. However, his Army mates knew him as "Nobby" after the character Nobby Walsh in the Sydney Telegraph cartoon strip "Joe Palooka".