Abarim Publications' online Biblical Hebrew Dictionary
The meaning of the root שכם (shkm) is unknown, but it yields one extant noun and a verb derived from the noun:
- The masculine noun שכם (shekem) means shoulder (Genesis 49:15) or sometimes the whole back (1 Samuel 10:9, Psalm 21:12).
- The denominative verb שכם (shakam) means to rise early, or to make an early start (Genesis 19:27, Joshua 8:14).
What the noun and the derived verb have to do with each other is open to conjecture. BDB Theological Dictionary thinks that early in the morning camp was broken and all elements were hoisted upon the shoulders of man and beast.
HAW Theological Wordbook of the Old Testament peers a bit deeper into the matter and notes that in Scriptures a rising early most often has to do with the diligence/ persistence of the riser (to get a good start of the day; note that the noun שחר (shahar), meaning dawn yields the denominative verb שחר (shahar) meaning to seek diligently), and so does the carrying of an actual load or a task or position upon the shoulders.
The prophet Isaiah states that Eliakim, who was king Hezekiah's chief housekeeper (2 Kings 18:18), would become a father to the house of Judah, typically by saying that the key to the house of David would be on his shoulder (Isaiah 22:22). In that same tone, Isaiah predicts the birth of the Messiah, "and the government will rest on His shoulders . . . " (Isaiah 9:6).