Early 20th century; earliest use found in American Naturalist. From scientific Latin Peridinium, genus name (C. G. Ehrenberg Organisation, Systematik u. geographisches Verhältniss der Infusionsthierchen ii. 74/2; from Hellenistic Greek περιδινής whirled round (from ancient Greek περι- + δίνη circular motion, something which rotates or whirls round (of uncertain origin); compare ancient Greek περιδινεῖν to whirl round) + scientific Latin -ium: see -y) + -an.