shoulder n.

"region around the joint where the arm connects to the trunk of the body," Middle English shulder, from Old English sculdor "shoulder of a person," from West Germanic *skuldro (source also of Middle Dutch scouder, Dutch schouder, Old Frisian skoldere, Middle Low German scholder, Old High German scultra, German Schulter), a word of unknown origin which is perhaps related to the source of shield (n.).

Figuratively, "sustaining power, strength to support burdens," in Old English. The meaning "edge of the road" is attested from 1933. Shoulder-blade "the scapula" is by c. 1300. Shoulder-length, in reference to hair, is from 1951. Shoulder-strap (n.) is by 1680s. To stand shoulder-to-shoulder (1580s) originally was of soldiers in formation. Phrase over the shoulder, indicating ironic statement, a meaning the reverse of what is being said, is by 1590s. To cry on (someone's) shoulder in the figurative sense is by 1935.

c. 1300, shulderen, "to push with the shoulder," from shoulder (n.). The meaning "take a burden" (as upon the shoulders) is attested by 1580s. The military sense of "carry (a musket) upright and resting against the hollow of the shoulder" is by 1590s. Related: Shouldered; shouldering.