Ḥijā j refers to the bony structure around the eye; kahf is a cave, and qalt is a rock hollow capable of retaining water. These terms jointly portray eyes set within a deep, protective framework.
Istakannatā is a dual feminine verb referring to the two eyes; its formation belongs to the istafʿala pattern. The mirrored brightness and the sheltered rock-cave image complement rather than duplicate one another.