Top sixteen strokes form the
薛-shape, here functioning as a phonetic shell: xuē drifted heavily to niè through tone and onset shift. Historically this top was a related grass+
辛 cluster meaning 'offshoot of a tree stump,' which still echoes in
孽 — an illegitimate offshoot of a family line. The visual match with
薛 is coincidence at the modern stage.