Dami
Damian didn't understand why so many "family members" were inclined to use only half his given name. His first thought had been sheer laziness, but he had eventually dismissed that theory based on their varying levels of activity when using the diminutive. He had also dismissed the theory that it was mockery, having done extensive research into the word "Dami" in every language he knew of and finding nothing worthy of mocking.
Despite Grayson's insistence, it could not be affection: even Drake used it on occasion.
Even if it was, affectionate nicknames were unnecessary and inappropriate. Mother always said so.
Poor Damian, genuinely baffled by affection and nicknames and, you know, family.