I found it, actually it runs about three pages in Cold Days from 417 to 420, and it is all about a battle being waged in Harry's mind. When Harry is giving his name, it is in a form of attack, he isn't worried about his name being used, he is totally pissed off and he wants to draw Shark Face out to reveal who Itself really is.. In other words Harry is under a psychic attack from Shark Face and he has had enough.
Page 417 Cold Days.
And I'd be damned if I was going to roll over for some punk Outsider and his psychic haymaker.
The words first. Damned near everything begins with words.
Harry struggles to get the words out at first then;
And I laughed. As if some freak who had never loved enough to know loss could tell me about pain.
"I AM HARRY BLACKSTONE COPPERFIELD DRESDEN!" I roared.
Then all hell begins to break lose, Harry feels free from all restraint, even he dismisses the image of Mab hanging over him.
Harry says further;
Sharkface had chosen a battle of the mind. So be it. My head, my rules.
Images of more hell breaking lose, scarlet lightning, earth and staff come into play. Then Harry furthers the challenge.
"Okay big guy," I snarled out of the dark will that even now gathered itself to attack again."Now we know who I am. Let's see who you are."
Very clear, Harry isn't at all worried that his name is going to be used against him,
Next page, Harry states why he used his name; 418
"Thrice I command thee!" I shouted focusing my will, sending it coursing into my voice, which boomed out over the landscape. "Thrice I bid thee! By my name I command thee: Tell me who you are!"
Then the Outsider appears and speaks it's name;
I AM GATEBREAKER, HARBINGER!
I AM FEARGIVER,HOPESLAER!
I AM HE-WHO-WALKS-BEFORE!
Harry is a bit shocked and surprised that his ploy worked. Suddenly he understood what the Outsider was about..
Using, no doubt, the insight gifted him by his mother back in that soul gaze with Thomas back in Blood Rites. Harry understood It was an Outsider, he further understood that when he battled HE WHO WALKS BEHIND when he was 16, that It was trying to shape him, but he didn't know what for. He goes on on page 419 What is interesting is he compares this Outsider to Mab with his insight.
It was huge, powerful, and in a way utterly different from the kinds of power I had seen before. This thing wasn't bigger
than Mab. But it was horribly, unbearably deeper than her. like a photograph of a sculpture compared to the sculpture itself. It had power at It's command that was beyond anything I had seen, beyond measure, beyond comprehension--just plain beyond.
On one hand Harry knows It is beyond any power he has, but then he realizes It has no power over him either. He refers to himself as a grain of sand on a beach. The grain of sand isn't impressed with the power of the ocean, and neither is he impressed with the power of this Outsider. He goes on and concludes with;
"Bring it on!"
The attacking voice or force in his head then retreats. Harry finds himself back on the motorcycle with Murphy as he has been the whole time the Outsider was attacking his mind. And on 420 we have the Erking saying;
"Well-done, starborn!"
I know my answer was long winded, but I think we have to view the whole scene in context, why Harry giving out his full name this time was so different from the past times when he feared to do it.