The Eyes Have It
The term “apple of my eye” has roots back to the King James Bible, but the modern sense of a highly favored person or object, goes back to the 9th century…still not too shabby in terms of long lineages. It was previously believed that the pupil of the eye was a solid object, and the term apple – another familiar sphere – came to describe it. Mind you, in these days effective eye care was in a primitive-to-nonexistent state, so eyesight was highly valued. Hence, the term lent itself to other things which were similarly precious.
The term “private eye” to describe private investigators has two plausible origins. The famous Pinkerton Detective Agency, which began in Chicago in the 1850s and was the original in the business in the US, used in their logo the image of a staring eye and the words “We Never Sleep.” However, the equally likely origin is simply the letter “I” in “private investigator.”
The adult eye color of a human baby is not always knowable at birth, as there are many genes and pigments still at work. In some babies, particularly lighter-skinned ones, it may take up to 3 years for the iris color to fully establish.