Isa. 9:6 is one of the best-loved verses we read at Christmas. I looked at it this morning in both the Hebrew and the Greek. Sometimes the Greek of the LXX is extremely literal. It reads a lot like an interlinear of the Hebrew text. Not so here.
Here's my translation of the Greek. As you can see, it is quite unlike what you're used to seeing when you read this verse in your English Bible:"For a child was born to us. A son, also, was given to us, whose rule is upon his shoulder. And his name is called Angel of the great counsel. For I will bring peace upon the rulers and health to him."
This is a reason why we must always compare the Greek LXX with the original Hebrew text. Let me see if I can figure out what's going on in the Greek translation. If I come up with something, I'll let you know.