What is the term for a commercial paper payable to bearer, i.e., to the person having possession of such?

The term that describes a commercial paper payable to bearer, meaning it is payable to the person who possesses it, is "Bearer Paper." Bearer paper is specifically designed to transfer ownership simply by delivery; anyone who holds the paper is entitled to the payment it represents without additional proof of identity or endorsement. This characteristic makes bearer paper unique and particularly advantageous in commerce because it facilitates easy and quick transactions.

In contrast, registered paper is tied to a specific owner's name and requires proper identification or endorsement for transfer, making it less flexible than bearer paper. Negotiable instruments encompass a broader category that includes both bearer and registered paper, along with other forms of documents like checks, but does not specifically refer to papers payable to bearer. Trust paper is a term that typically does not relate to commercial paper and involves fiduciary arrangements rather than direct payment terms. Therefore, the correct answer aligns with the definition and function of bearer paper in commercial transactions.