Voldemort's name

[kneazle255]

No: HPFGUIDX 82006


Kaome:
When DD encounters LV at the end of OoP, he calls him "Tom".  
(snip)
DD's slip up may not have occurred before that instance.
Assuming it was a slip up, which it may not have been.)
 
Geoff:
It might have been an attempt to re-establish some sort of empathy, 
or an appeal to his pre-Voldemort self. It might also have been to 
divert LV's attention away from Harry after the failed AK attempt.

Kneazle255:
I thought it was deliberate psychological warfare--DD trying to knock 
Voldemort off his game by saying something DD knew would upset him 
and very succinctly putting the Dark Lord in his place. Tom is facing 
his old teacher, and DD is pointing that out. It's Dumbledore 
saying, "I don't buy the fear you are trying to generate. I know the 
boy behind the mask. So you think you can take me, Junior?"