He doesn't understand why. But first names are always used as a weapon between them. Its strong, unyielding and so very personal. It hits home and they both know it. He uses hers to try to coax her, to pull her closer, into his heart and after he's learned all the ways she reacts to hearing it, the resigned huff, the shiver down her spine, it becomes a mightier weapon. She, on the other hand, uses his first name to pull him away. She uses it mockingly in the beginning, then to challenge him, dare him to speak up first, pushes him to the far edges of her heart. He tries not to seem too vulnerable when those situations occur. He won't let her see what it does to him, how it breaks him.
Hers translates into please, come closer.
His as a warning to back off.
But that night, we they both decide they're tired of chasing ghosts, tired of blaming each other and putting off everything life has to offer, after lingering kisses up against a wooden front door, the weapons disintegrate. First names becomes loving whispers and for the first time, take on a new meaning entirely.