jättämiensä
The word "jättämiensä" is a Finnish grammatical form. It is the genitive plural partitive of the past active participle of the verb "jättää," which means to leave. Therefore, "jättämiensä" literally translates to "of those having been left by them" or more commonly understood as "their leaving" or "the things they left behind."
This form is used when referring to something that belongs to, or is possessed by, multiple subjects
The usage of "jättämiensä" highlights a specific grammatical nuance in Finnish, where participles can be inflected