The first occurrence.
Until your brother’s anger turn away from you, and he forget what you have done to him: then I will send, and fetch you from there. Why should I be deprived also of you both in one day? Gen 27:45
The primitive root.
Strong’s H7911 שכח shakach, a primitive root meaning, “to forget, to ignore.” The 3-letter root is shin + kaph + chet.
shin ש = two front teeth, thus sharp, press, eat, two, again
kaph כ, ך = the open palm, thus bend, open, allow, tame
chet ח = the wall, thus outside, divide, half
The story: Breath passes through the teeth (shin) as an opening (kaph) in a wall (chet). When we forget something, it escapes us as breath escapes the body. How interesting, though, the implication that what we remember we keep enclosed behind a wall or a fortification.