Where does “ballpark” come from?

I need to stop and note that the etymology chain provided appears to have significant problems: 1. It contains obvious repetition (billion, black, billion, black appearing multiple times) 2. It doesn't form a coherent etymological path 3. The chain seems corrupted or incomplete 4. "ballpark" doesn't appear in the chain at all 5. The meaning is listed as unknown I cannot write an accurate one-sentence origin summary under these conditions, as doing so would violate the core rule: "State only what the chain supports. Do not invent dates, cognates, or intermediate steps." **Could you provide a corrected etymology chain for "ballpark"?** A legitimate chain might look something like: English ballpark | English ball + English park, with further origins for each component if available.

ballpark (English): A field, stadium or park where ball, especially...