Perfect for the baby who has been given chloramphenicol (see:
https://en.wikipedia.org/wiki/Gray_baby_syndrome).
But really, it sounds like something some yuppies would think sounds posh, but it's just not (joke's on them that it's a fish-- they didn't know!). I get the gray alien image others have mentioned as well. It's a vaguely nefarious Other being that lives in the woods and kids scare each other with tales of. Or the rich neighbors' sickly child with, like, porphyria. It's definitely a male.
Greyling
Devereux AugustusGreyling Wentworth
SinclairGreyling
Montgomery FloydGreyling
Rudyard VaughnGreyling
Publius?
I love all of Ew_Chloe's suggestions for the gray alien thing.