You are right regarding Yahgan being an agglutinative language and that words like 'mamihlapinatapai' is a result of that. But -- apologies for being nit-picky

You are right regarding Yahgan being an agglutinative language and that words like 'mamihlapinatapai' is a result of that. But -- apologies for being nit-picky -- your example does not fit that category. The German word 'Kugelschreiber' is just a compound (https://en.wikipedia.org/wiki/Compound_(linguistics) https://en.wikipedia.org/wiki/Compound_(linguistics)). The fact that compounds are typically written as a single word, as opposed to English, does not make German an agglutinative language; that is mostly a merely orthographic convention. German is considered a fusional (or inflected) language.