Ananda Coomaraswamy mentions the Logos Tomeus (Separating Word) of Plato in his letters. I am not sure why the writer of Hebrews would have had to read Plato - in that culture, Plato was part of the air that was being breathed by the soul.
Justin the Martyr:
"I shall give you another testimony, my friends, from the Scriptures,
that God begot before all creatures a Beginning, [who was] a certain
rational power [proceeding] from Himself, who is called by the Holy
Spirit, now the Glory of the Lord, now the Son, again Wisdom, again an
Angel, then God, and then Lord and Logos..."