A sea anemone; specifically one of the genus Actinia. Also (in form Actinia): the genus itself.
Valid publication of the genus name: Linnaeus Systema naturae (ed. 12, 1767) 1088; also used by Pallas (1766) for a genus of holothurian.
Mid 18th century; earliest use found in John Hill (bap. 1714, d. 1775), physician and actor. From scientific Latin Actinia from ancient Greek ἀκτῖν-, ἀκτίς ray + scientific Latin -ia.