Part 13 · Chapter 151

And the reason for the matter is that in the place where the hairs of the head end, which is the nape, there it is white, bare, without hair. And although the external ones and the shells (Kelipot) have all their hold on the back sides (Ahorayim) — for therefore they are called "other gods" (Elohim Aherim); understand this — and especially at the nape. And this is the secret of "for it is a stiff-necked people."