Pettigrew/Wormtail (was Transitions, etc Will the Real...)

[houyhnhnm102]

No: HPFGUIDX 167804

The argument over whether or not Snape would have known 
that Scabbers was Peter Pettigrew has got me to wondering 
again, why does Voldemort address Pettigrew as "Wormtail"?  
There's something about that strikes a wrong note with me 
every time I read GoF. Would Pettigrew have introduced 
himself as "Wormtail" when he first went over to the Dark side? 

It is not a very flattering nickname, although I suppose 
it would be difficult to come up with a nickname for a rat 
that was complimentary (Cheddar or Whiskers would at least 
be a little more neutral).

Its use by the Marauders seems to reinforce Peter's low 
status tag-along position within the group.  I can see 
him enjoying being called Wormtail by James, Sirius, and 
Lupin because it signified his acceptance by those three, 
even if he was at the bottom pf the pecking order, but I 
can't see him wanting DEs to call him that. Voldemort 
clearly uses it in a way that is derogatory, as if to 
rub it in that Peter is a coward who betrayed his former 
friends.  

It just stikes me as odd that Peter would volunteer the 
information.  How did Voldemort learn the nickname?  
Perhaps by the use of Legilimency?

houyhnhnm