Northuldran naming conventions
Considering that the Northuldrans are based on the Sami people, the Northuldran characters should have Sami names. They obviously do not. Why is that?
The simplest explanation would be – this particular aspect of the Sami culture was not included in the adaptation.
Another possibility is that the Northuldrans do, in fact, have indigenous names, but only use those amongst themselves, giving the outsiders commonly accepted equivalents, which are easier to pronounce/remember.
Going even further than that – If we operate under the assumption that Arendelle is a Scandinavian state, their Native language is some sort of Scandinavian, and all the characters’ names have been adapted for the benefit of the English-speaking audience, the English dubbing of the movie may not be entirely correct when it comes to pronunciation of names.
Therefore, the Sami equivalents of the Northuldran names could be:
Iduna – Iiddá, Iinná (or she was named after the goddess Iðunn, in which case “Iduna” may have simply been the Northuldran version of Iðunn to begin with)
Honeymaren – Hánna Máren (or she started off as Máren and the “Honey” part was added later in life as a title, something like “Máren the Honey”)
(This is a crazy idea, but at hopefully it will entertain you ^_^)