The derogatory meaning of the word is US-specific. To the rest of the world, Nimrod is simply the mythical character. Nimrod's author is German. It's not surprising that he wasn't aware of the American slang usage.
Is Nimrod mentioned in any historical texts outside of the Bible? It seems like Bible trivia that very few people would know, perhaps especially outside of the US.
He was kind of a big deal in the Old Testament as a Baddie and Wikipedia says his story was well-known, especially in Islam and Judaism.
> The story of Abraham's confrontation with Nimrod did not remain within the confines of learned writings and religious treatises, but also conspicuously influenced popular culture.