'Shoulder' is purely Germanic with no certain deeper etymology — a common body-part mystery.
The joint connecting the arm to the torso, or the upper part of the back between the neck and the upper arm.
From Old English 'sculdor' (shoulder), from Proto-Germanic *skuldrō (shoulder). The further etymology is debated but may connect to PIE *skel- (to cut, to split), possibly referring to the shoulder blade as a flat, split-off piece of bone — the scapula being one of the most distinctive flat bones in the human skeleton. An alternative proposal links it to PIE *(s)kel- (to bend, to curve), referring to the rounded shape
The phrase 'cold shoulder' — meaning a deliberate snub — may derive from the practice of serving a guest a cold shoulder of mutton instead of a hot meal, signaling that they had overstayed their welcome. This folk etymology was popularized by Sir Walter Scott in 1816, though some etymologists dispute the culinary origin and believe it simply refers to literally turning one's cold shoulder toward someone.