The apple of one's eye

This evocative phrase . . . [is] . . . almost as old as the language, since the first recorded examples can be found in the works of King Alfred at the end of the ninth century.

At this time, the pupil of the eye was thought to be a solid object and was actually called the apple, presumably because an apple was the most common globular object around. So the apple of one’s eye was at first a literal phrase describing the pupil. Because sight was so precious, someone who was called this as an endearment was similarly precious, and the phrase took on the figurative sense we retain. King Alfred actually uses it in this way, and presumably it wasn’t new then.

Our modern word pupil, by the way, is from Latin and didn’t appear in English until the sixteenth century. It’s figurative in origin, too, though in a more self-obsessed way. The Latin original was pupilla, a little doll, which is a diminutive form of pupus, boy, or pupa, girl (the source also for our other sense of pupil to mean a schoolchild.) It was applied to the dark central portion of the eye within the iris because of the tiny image of oneself, like a puppet or marionette, that one can see when looking into another person’s eye.

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