Bly in Swedish. But we add some weirdness to the Bly part so a "lead pencil" is blyertspenna ("penna" meaning pencil). I can't think of another word where that specific addiction is used, and I have no idea what it means.

That would explain why a pencil, which contains a "lead" (actually a polymer or graphite now) is Bleistift

Also the language is called English. By default, the English are doing it right and anything else is wrong. Maybe better, the argument can go for decades longer, but if anyones wrong its everyone else.