This makes me deeply curious about how LLMs understand language. Do LLMs relate cognates more than words that are dissimilar in different languages? I wonder if that plays some role in the effectiveness of tokenization.
The grammar is perhaps more likely to help. Similar word order etc. Even weirdness like German - my only top grade on a German essay in school was one where I on purpose ignored what I thought I knew about German and tried to evoke "old fashioned" Norwegian. The result was guessing at a bunch of grammatical structures that I didn't know if was valid German. Turned out I was right about most of it - century old Norwegian was far closer to century old Danish, was a lot closer to valid German, and enough so to impress my teacher enough to overlook a number of orthographic mistakes.
"What sayest thou?" -> "Was sagst du?"
In fact, for the above, you don't even have to know a single German word. You just have to know what for question words, "wh" -> "w", that the English "y" at the end of a syllable usually comes from an older Germanic "g" sound, and that "th" was replaced by "d" in German. That gets you 90% of the way from early modern English to modern German in the above example.