Knuckle

Knuckles are the joints of the fingers and toes of humanoid species. Monkeys and apes also have knuckles.

When Wendy tried to convince Luther Fenwick to sit down with Doctor Pelagian to talk about how to stop pollution, he asked her if she expected him to "knuckle under to blackmail.

Appearance
Super Friends
 * Season 1: Dr. Pelagian's War