I should also say that the thought in Justin Martyr is more advanced than that of Paul. Justin positively identifies the Son with the Lord God of the OT. The thought in Paul is more primitive; Paul simply does not distinguish the Son from the Lord God of the OT.
Jehovah is the name of "the Father" clearly.
http://www.watchtower.org/e/bible/ps/chapter_110.htm#bk1
But the divine name called Jehovah means "I AM."
And Jesus is "I AM."
But it does not mean "The Father is the Son."
That is, it is not the meaning "Jehovah is Jesus."
Excepting the modalists (none of thom are represented in the NT or in the early patristics), no one who thought that the Lord God of the OT was Jesus believed that the Father is the Son. Justin specifically denied that the Lord God of the OT was the Father. Paul distinguished the Son from the Father and still did not distinguish the Son from the Lord God of the OT.