The name Reyn is of American origin and is a gender-neutral name meaning "Rule." In fluid dynamics, the "reyn" is a British unit of dynamic viscosity, named in honor of Osbourne Reynolds, for whom the Reynolds number is also named. The relation between the reyn and the poise is approximately 1 reyn = 6.89476 × 104 P, and in SI units, viscosity is expressed in newton-seconds per square meter, or equivalently in pascal-seconds, with the conversion factor being approximately 1 reyn = 6890 Pa s. The name Reyn carries the significance of rule and authority, reflecting strength and leadership. It is a unique and meaningful name with a rich history in both American culture and the field of fluid dynamics.