One possible explanation for Din Grogu is that the Armorer is honoring a naming tradition on Din's homeworld from before he became a Mandalorian. In many real-world cultures, the family name is what comes first, then the name of the individual, so it's possible Din has been the character's real surname the whole time. Another possibility is that this naming system is unique to the Children of the Watch, or that the Armorer is establishing it as a unique trait of Din and Grogu's clan of two. Several Mandalorian factions have their own unique customs, so Din Grogu's new name could reflect that, but for now none of these explanations are confirmed.