knock, extort

敲 is composed of 高 (high) and 攴 (strike). 高 is a pictograph of a multi-storied tower, representing height, while 攴 depicts a hand holding a club-like weapon, implying a light strike. Thus, 敲 signifies striking or knocking on a tower with a weapon, originally meaning to knock or tap. People living in high towers were often wealthy, and if threatened with force, they might hand over valuables, so 敲 also carries the meaning of extortion or blackmail.