What does Boxing Day have to do with boxing?
Old English sculdor "shoulder," from West Germanic *skuldro (cf. Middle Dutch scouder, Dutch schouder, Old Frisian skoldere, Middle Low German scholder, Old High German scultra, German Schulter), of unknown origin, perhaps related to shield (n.). Meaning "edge of the road" is attested from 1933. Cold shoulder (Neh. ix:29) translates Latin humerum recedentum dare in Vulgate (but see cold shoulder). Shoulder-length, of hair, is from 1951.
c.1300, "to push with the shoulder," from shoulder (n.). Meaning "take a burden" first recorded 1580s. The military sense is from 1590s. Related: Shouldered; shouldering.
shoulder shoul·der (shōl'dər)
The joint connecting the arm with the torso.
The part of the human body between the neck and upper arm.
A wild guess or try; an attempt that has little chance of success
in anatomy, the joint between the arm, or forelimb, and the trunk, together with the adjacent tissue, particularly the tissue over the shoulder blade, or scapula. The shoulder, or pectoral, girdle is composed of the clavicles (collarbones) and the scapulae (shoulder blades). In humans the clavicles join the sternum (breastbone) medially and the scapulae laterally; the scapulae, however, are joined to the trunk only by muscles. In many cursorial (running) mammals the clavicles are reduced or no longer present, which permits free movement of the humerus (upper arm bone) in a forward direction. The major joint of the shoulder is the glenohumeral joint, a ball-and-socket joint in which the humerus is recessed into the scapula. The flexibility of the shoulder has permitted various locomotor adaptations, such as digging (in moles), running (in antelopes), brachiation (in gibbons), and flight (in birds).