Keep me as the apple of the eye, hide me in the shadow of Your wings,
RADAK
1. Keep me as the pupil (אישׁון) of the ball of the eye:
As a man guards the pupil of his eye – that is, the black part through which the light (passes). It is called the אישׁון (lit. little man), because the image of a man is seen in it; and the waw and nun mark the diminutive, because the image is diminutive;
Rabbi HIRSCH
1. [אִישׁוֹן] (ishon)
Derived from [ישן]
is “old”, “dull”, “black”, “dark”, or “that which is dark.”