[student], late 14c., "orphan child, ward, person under the care of a guardian," from Old French pupille (14c.) and directly from Latin pupillus (fem. pupilla) "orphan child, ward, minor," diminutive of pupus "boy" (fem. pupa "girl"), probably related to puer "child" (and thus probably from a suffixed form of PIE root *pau- (1) "few, little").
Meaning "disciple, student youth or any person of either sex under the care of an instructor or tutor" is recorded by 1560s. Related: Pupillary; pupillarity; pupillage.
"center of the eye, orifice of the iris," early 15c. pupille (the word is in English in Latin form from late 14c.), from Old French pupille (14c.) and directly from Latin pupilla, originally "little girl-doll," diminutive of pupa "girl; doll" (see pupil (n.1)).
The eye region was so called from the tiny image one sees of oneself reflected in the eye of another. Greek used a single word, korē (literally "girl;" see Kore), to mean both "doll" and "pupil of the eye;" and compare obsolete English baby "small image of oneself in another's pupil" (1590s), source of 17c. colloquial expression to look babies "stare lovingly into another's eyes."
Self-knowledge can be obtained only by looking into the mind and virtue of the soul, which is the diviner part of a man, as we see our own image in another's eye. [Plato, Alcibiades, I.133]