Because you’re all awesome, here is a bonus piece of information: Selkie’s people come from a sovereign city-state. Location and name as yet unknown. However… the symbol within Selkie’s Mom’s speech bubble is the symbol OF that city-state. 🙂
I feel like Selkie's other language is something Marta and Antoine would have been told about behind the scenes when Theo and Marigold were preparing them for the meeting. Todd knows of it's existence simply from living with Selkie the past few weeks.