There's not much information in terms of relation to other Nordic myths. Mostly just connected with varying sailors.
I don't think the Jotuns are necessarily Outsiders themselves. But perhaps they are related/connected like the Fomor and the Outsiders are.
That's confirmed in one of the short stories. Sigrun calls the Fomor cousins of the Jotuns.Indeed, it is mentioned a few times. But I wonder if there is an Outsider crossover on the venn diagram. I mean, by cousins it could mean that the Fomor are sort of scions of Outsiders...or it could mean that both the Fomor and the Jotuns are both scions (or somehow related) to the Outsiders. Or something else entirely of course.
And Harry found a 3 foot long footprint on the beach.Yeah, definitely not Ethniu's I think. More likely one of her bruisers.