"Fidelius" etymology (Was: MuggleNet - Godrics Hollow Theory)

[justcarol67]

No: HPFGUIDX 163542

Kemper wrote:
<snip>
> bboy was saying that:
> 
> "The Potter's trusted Peter with their lives, and in accepting that
> trust, Peter is implying a true and deep loyalty to the Potters."
> 
> I read this to mean that bboy believes the Fidelius Charm works (in
part) by the loyalty Peter feels of the Potters.  I disagreed because
I don't believe that Peter was loyal to the Poters at the time of the
charm.  Therefore, IMO, the charm must not rely on the loyalty (from
Old French /loial/, from Latin 'legalis' /legal/, from 'lex' /law/) of
the Secret Keeper.  Rather, it relys on the faith (from Old French
'feid', from Latin 'fides' /trust, belief/) of the Secret Teller.
> 
> Peter has the Potters' faith, not the Potters' loyalty.
<snip>

Carol responds:
Sorry to snip your Frost parody or whatever you want to call it, but I
think it's the Latin, not the English, etymology that's relevant here,
not so much "fides" (faith) as 

fidelis -e [trusty , steadfast, faithful]; m. as subst., esp. pl.,
[confidants, faithful friends]. Adv. fideliter, [faithfully; securely,
without danger].

fidelitas -atis f. [faithfulness, trust, fidelity].

http://www.archives.nd.edu/cgi-bin/lookup.pl?stem=fidel&ending=

While I believe that the Fidelius Charm was broken when the Secret no
longer existed, certainly by the time the house was destroyed (when
two Potters were dead and the other was lying in the rubble), hence
"The Potters are hiding at [address] Godric's Hollow" was no longer
true, it's possible that the moment they were revealed to Voldemort
was the moment that the charm was broken because at that moment the
Secret no longer existed--the person they were hiding *from* could see
them. If that's the case, PP's breaking the faith imposed in him,
broke the charm.

To be sure, he was never "trusty, steadfast, faithful," or at least he
had ceased to be so long before the Secret was concealed in him, but
revealing the Secret to Voldemort, the enemy from whom the Potters
were hiding, was a breach of fidelitas (faithfulness, trust,
fidelity), the trust the Potters placed in him. Far from acting
"faithfully" and enabling the Potters to live "securely, without
danger," he destroyed their safety and security by his breach of
confidence and trust.

So the betrayal itself, the revelation of the Potters in their hiding
place (I'm sure that PP brought Voldemort to the spot, said something
like "There they are; that's their house," and transformed into a rat
to watch the action) may have been enough to break the Fidelius Charm
(and alert Dumbledore to their danger). What I'm sure of is that the
Charm was broken, enabling DD not only to know where they were but to
inform Hagrid of the address, either by the betrayal or by the deaths
of the adult Potters and the exposure of Harry to danger, or by the
destruction of the house. By the time Voldemort had exploded, taking
the house with him, there was no Secret to keep. Etymology suggests
that it was the betrayal that broke the charm.

Carol, not really arguing with Kemper but trying to understand how the
charm works in relation to its name