Every time Deidara called out "Sasori", "Danna", or any combination of the two, Sasori came. He might come quietly, or he might come swearing and angry, but he came. That was all the mattered. After the Battle, Deidara called for Sasori, but he didn't come. Deidara tried again and again, but he never came.
Eventually Deidara stopped saying His name. He didn't want to be reminded that Sasori would never come back. His was simply known as, "My former partner." His current partner, Tobi, made him long for Sasori more, but he never said His name.
As he lay barely alive, most of his body destroyed his last fleeting thought was, "Sasori-danna…" And, to his surprise, there stood Sasori.
"I knew you would come, Danna!" Sasori only extended his hand and said, "Let's go home, Deidara."
--
For my Dei-kun.