pinna

The word 'pinna' entered English directly from Latin in the late 17th century, where it originally meant "feather" or "wing." This Latin term is thought to derive from a Proto-Indo-European root meaning "feather" or "hair," conceptually linked to things that are thin, projecting, or fringed. The anatomical sense, referring to the projecting part of the outer ear, developed from the Latin meaning of a "fin" or a "small wing," metaphorically extending to any thin, projecting flap. In botany, its application to a leaflet or primary division of a fern frond similarly draws on this core idea of a feather-like projection or segment.

The word 'pinna' is a simplex loanword from Latin. In Latin, 'pinna' meant "feather, wing, fin, battlement" (from the notion of a projecting part). Its functional role is as a complete, unanalyzable noun stem in English.