No, it's not. You've been living in a town that just went through a massive nine day battle to survive a Chaos invasion, and Boris is the guy who stopped the invasion. Your character would damn sure have heard of Boris. Every person would be talking about him and his heroics. The initial post makes clear you know who won the battle at Middenheim, as well.
So no, Untergard isn't an out-of-the-way town, and you would know it - it's in the middle of the Storm of Chaos, and it's the place that broke Khazrak One-Eye's forces.