From: Robyn, Duke of Amber

fic-wise this "could" be what Belldandy could call Kietchi's

 um...dingus.
 the angel's "little devil"<<

I'd think she might use something like 'Keiichi-ken' or 'ichi-ken'. That is
if she even cares. Keiichi is... Keiichi. That's all that matters to her.