手首
てくび · tekubi · JLPT N2 · noun
wrist
手 (te) hand + 首 (kubi) neck: the hand's neck, where it joins the arm
首 (kubi) means neck, the same word used for a person's neck. Tekubi is the neck of the hand, the narrow joint between the hand and the forearm.
手 — pictograph of a hand with five fingers
手 is a pictograph showing an open hand with fingers and a wrist. Early bronze and oracle bone forms clearly depict five splayed fingers, which simplified over time into the modern shape. It keeps its original meaning of 'hand' and also serves as a radical in many characters related to hand actions.
首 — hair 丷 over face 自 (eye + nose)
首 is a pictograph of a head, originally drawn with hair on top and a face below (containing the eye element 目). It meant 'head' literally, then extended to 'chief, leader, first' since the head is the topmost and foremost part of the body.