Commentary for Leviticus 13:41

ואם מפאת בניו AND IF FROM THE CORNER OF HIS FACE [THERE FALLS OFF THE HAIR OF HIS HEAD] — The area from the slope of one’s skull in the direction of the face is called גבחת (and that explains why the man suffering from such a malady is here called גבח) — and the temples on both sides are also included; and the area from the slope of one’s skull in the direction of the back of his head is termed קרחת (hence the term קרח in v. 40) (Sifra, Tazria Parashat Nega'im, Chapter 10 7).