Eridians have a full name that they introduce themselves with and use formally, and it’s very long because it includes details like their occupation, role in society, and their lineage. And, once Grace is on Erid, it’s decided by Rocky and the Eridian officials that Grace needs a full Eridian name, because it’s odd to just call him Grace in certain situations. It is easy to figure out part of his new full name, adding in teacher and savior of the stars, but the lineage bit is a little tricky. Grace was never particularly close to his parents so that doesn’t feel right, and he doesn’t feel like attempting to translate their names into Eridian. In the end, for that section, he just adopts parts of Rocky’s and Adrian’s names because that’s really his new family.
On his first excursion out of his biodome and through Erid (because of course they made him his own xenonite suit) with Rocky and Adrian, they get approached by many other Eridians who have heard of Grace. They coo some and praise the human, and add a congratulations to Rocky and Adrian at the end. It takes this happening a few times before Grace picks out the Eridian word for baby or child in the congratulations, and he’s ECSTATIC, making the assumption that his friends must be having a baby. Of course, he has some questions like “Why didn’t you tell me sooner?” and “Why does everyone know but me?” and “When will they be here?” and “Actually, how do Eridians reproduce?”. During his barrage of questions, Rocky and Adrian are speaking to each other in low tones, trying to figure out the best way to tell Grace that the name he uses for introductions and official matters translates to Grace, Child of Rocky and Adrian, Teacher and Savior of the Stars.
The other Eridians figure that thirty Earth years and then some is awfully young to tragically no longer have parents, and it’s very kind of Rocky and Adrian to take in a child of an alien species and raise it as their own. Especially since Earthlings don’t seem to take good care of their young, sending them into space.