In Scott Turow's legal mystery The Last Trial, the point of view character is an old man. Pinky is his grand-daughter. The following passage occurs near the end of the book:
Pinky says nothing to him [Lep], but instead strikes one index finger against the other, as if making fire. The gesture seems comical, but Lep stops cold when he takes in the fierce look Pinky is giving him.
What is the meaning of this gesture? Is it something that only young people would be acquainted with?