I always thought the gesture resembled "whittling," and in a lesson about Alaskan totem poles, I came across the "shame pole" or "shaming pole." These poles were carved out of huge logs to publicly embarrass individuals deemed to have committed behavior they of which they should be ashamed. One of the most famous examples is the Seward Shame Pole located in Saxman, AK, near Ketchikan. I don't know if the gesture is actually connected to the carving of poles, but my students felt it was a reasonable association.