English: Why did he call him “son of Nachor” and not “son of Besuel”? To teach you that a wicked person is called after his wicked grandfather.
On the daf / in context: The midrash notes the unusual patronymic and derives a principle about naming the wicked after their wicked ancestors.
Type of Learning
Derash on the verse (midrashic) — not a formal named middah of the 13. The choice of grandfather rather than father is taken as deliberate characterization.
What Is Learned
A wicked person is identified with his wicked forebear; Lavan is linked to Nachor rather than to Besuel.