Patronus: Not Just for Dementors Anymore?

[Charme]

No: HPFGUIDX 124033

I've been half rereading sections of PoA because of some of the threads here
lately, and I'm wondering if anyone else is as curious as I am about the
Patronus Charm. We have it from Fantastic Beasts that Flavius Belby survived
a Lethifold attack by casting a Patronus against it, and then we find that
the same charm works in repelling Dementors. Curious, but this would lead
one to speculate what the Patronus was used for prior to old Flavius
executing the effectiveuse of it against a Lethifold. (And for those of you
without FB, Flavius tried a Stunning and an Impediment hex on the Lethifold
prior to trying a Patronus)  Lupin says it is "ridiculously advanced" and
that even qualified wizards have problems with it. How interesting this
statement is, when you compare it to references to OoP, where Harry,
Hermione, and Cho we know have produced a corporeal Patronus, although
admittedly Harry's the only one to do so under duress. The Patronus is
described as "silvery" for the most part, and if you're wondering why I'm
pointing that out, bear with me and I promise I'll get to that. :)

Where this all gets interesting is in OoP, where other spells and charms
have that same "silver" description. For example, thoughts which are put in
the Penseive are described as  One is in DD's office when Umbridge busts the
DA:

"A streak of silver light flashed around the room; there was a bang like a
gunshot and the floor trembled; a hand grabbed the scruff of Harry's neck
and forced him down on the floor as a second silver flash went off; several
of the portraits yelled, Fawkes screeched and a cloud of dust filled the
air"

And then again in the DoM:

One of the Death Eaters shot their own Stunning Spell at Neville; it missed
him by inches. Harry and Neville were now the only two left fighting the
five Death Eaters, two of whom sent off streams of silver light like arrows
which missed but left craters in the wall behind them."

There's also the shining "silver" shield LV produces when dueling with DD.
I'm not sure, but I suspect that these silver charm and spell descriptions
all deal with more advanced magic in the class of the Patronus Harry will
need to learn or master moving forward in HBP and beyond.  However, this
brings us full circle with the Patronus: what *exactly* was the spell for
before the first known record of its use against a Lethifold? What (or who)
else will it repel and how?

Things to make you go hmmmm......

Charme