An Etymological Dictionary of Astronomy and Astrophysics

1. In the → eye, the apparently black opening in the center of the → iris that permits light to pass and be focused on the → retina.
   

2. In a → lens, the → image of the → aperture stop as seen from → object and → image space. Same as → entrance pupil.

Etymology (EN): From M.E. pupille, from O.Fr. pupille, from L. pupilla, originally “little girl-doll,” diminutive of pupa “girl, doll” (Fr. poupée), so called from the tiny image one sees of himself reflected in the eye of another.

Etymology (PE): Mardomak “little man,” the allusion being to the tiny image of himself reflected in the eye of another, from mardom “man, human being, mankind, people;”
→ people, + diminutive suffix -ak.