Adam Clarke on Isaiah 9:6

The government shall be upon his shoulder - That is, the ensign of government; the scepter, the sword, the key, or the like, which was borne upon or hung from the shoulder. See note on Isa 22:22.

And his name shall be called - אל גבור El gibbor, the prevailing or conquering God.

The everlasting Father "The Father of the everlasting age" - Or אבי עד Abi ad, the Father of eternity. The Septuagint have μεγαλης βουλης Αγγελος, "the Messenger of the Great Counsel." But instead of אבי אד Abi ad, a MS. of De Rossi has אבעזר Abezer, the helping Father; evidently the corruption of some Jew, who did not like such an evidence in favor of the Christian Messiah.

Prince of Peace - שר שלום sar shalom, the Prince of prosperity, the Giver of all blessings.

A MS. of the thirteenth century in Kennicott's collection has a remarkable addition here. "He shall be a stumbling-block, המכשלה; the government is on his shoulder." This reading is nowhere else acknowledged, as far as I know.