Etymology: < post-classical Latin pinna (6th cent., and in some early editions of Pliny), variant of classical Latin pīna (Cicero, Pliny) < Hellenistic Greek πῖνα, ancient Greek πίνη (also πίννα, πίννη, though not in inscriptions or papyri), of unknown origin, perhaps a Mediterranean loanword. Compare Middle French, French pinne (1558; rare before 18th cent.; now usually pinne marine (1712)), Italian pinna (1476).

Etymology: < post-classical Latin pinna (1651 in the passage translated in quot. 1668 at sense 1a; 1572 or earlier in sense 1b; 1686 in sense 3), specific uses of classical Latin pinna feather, wing, fin, raised part of a battlement, perhaps originally a regional variant of penna feather (see pen n.³); the two forms occur in all senses in inscriptions and manuscripts. Compare Middle French, French pinne (1532 in sense 1a; 1558, and subsequently a1788 in Buffon, in sense 2a), Italian pinna (15th cent. in sense 2a, 1585 in sense 1b, 1681 in sense 1a).It is likely that the architectural sense of the Latin word arose in military slang by analogy with the plume on a helmet.