Exodus 28:12

28:12 You are to put the two stones on the shoulders of the ephod, stones of memorial for the sons of Israel, and Aaron will bear their names before the Lord on his two shoulders for a memorial. ¹ 

Isaiah 22:22

22:22 I will place the key ²  to the house of David on his shoulder. When he opens the door, no one can close it; when he closes the door, no one can open it.

¹ sn This was to be a perpetual reminder that the priest ministers on behalf of the twelve tribes of Israel. Their names would always be borne by the priests.

² sn This may refer to a literal insignia worn by the chief administrator. Even so, it would still symbolize the administrator’s authority to grant or exclude access to the king. See J. N. Oswalt, Isaiah (NICOT), 1:422.