Two juxtaposed nouns indicate a genitive-type meaning for the first, so we'd call this "great houses' writing", colloquially the outlines of great houses.

I love that!

Thank you for doing this - it is all so utterly fascinating! I love how you arrived at the word for "mansions", too, and used a non-native word form to get to a more poetic expression of "writing". Such cool ways of thinking about language.

(And I really can see my highly beloved Inkburrow font in your Amíu handwriting! :)