People are often a bit confused about this expression. First, the expression itself is NOT from Hebrew as you may sometimes be told (there is no mention of an "apple" in the Hebrew expression). It is simply an Old English expression for the pupil (attested from the 9th century). BUT the way we now use the expression -- to refer to someone or something very PRECIOUS to us -- IS the result of its appearance in English Bible translations. Specifically, four verses in the Old Testament (Deuteronomy 32:10; Psalm 17:8; Proverbs 7:2; Zechariah 2:8) refer to regarding or protecting someone else as one would protect the pupil of one's own eye... except that older English Bible translations used the common Old English expression "apple of my eye" to translate these verses. But at the same time these translations were appearing (mainly in the 16th century), English expression for the body part started to fall out of use, replaced by "pupil" (a Latin word with its own interesting history). As a result, the expression itself began to be thought of as a "biblical expression", and began to be used as if it meant "something precious" (an idea that fit the teaching of those biblical verses), the usage we now know. ---------------------------- As for the Hebrew -- the popular claim, first suggested by a medieval Jewish commentator, that the Hebrew expression being translated literally mean "little man of the eye" is understandable (since the word "ishon" looks a lot like Hebrew "ish" meaning "man") but doubtful. Elsewhere the word simply refers to something that is very dark. Thus the literal meaning is simply "dark part of the eye". (Some Hebrew grammars list the ending -on as a diminutive form, but the ONLY evidence they provide for such a form is this word itself! I call that a circular argument.) On the other hand, the Latin pupil DOES have a meaning like this. The word is from Latin for "doll", the notion being that when you look in someone else's eye you see a reflection of yourself that looks like a very small person or doll.