Johnston's paper does not explain the choice of the name, but ancient Greek σπινθήρ means "spark." In images of the living animal, it appears to be surrounded by a cloud of pinpoints of light.[3][4]
^Yamamoto, R.; Imajima, M. 1985. A new species of the genus Spinther (Polychaeta, Spintheridae) from Japan. Bulletin of the National Science Museum Series A (Zoology) 11(3): 129-135