Why did Tress say...?

So I finished Tress of the Emerald Sea today and I the enjoyed the book. All of the Cosmere connections are great. However, one stood out that I couldn't understand. Maybe I'm missing something.

In one part of the book, Tress is referring to Death with nails in his eyes. I imagine that is a reference to Ironeyes/Marsh from Scadrial. But how? She was not Cosmere aware up to that point. Why would the people of Lumar have the same image of death as a planet that don't know of?