There is an idea in Christian (Catholic?) theology that the Devil can
speak unknown languages and/or dead languages. This idea has been
represented in many Hollywood movies, including The Exorcist and The
Devil's Advocate. I am looking for the origin of this idea. Who first
came up with it? When? Is there a part of Scripture they interpreted
to come with it? If so, specifically what passages did they use to
support this idea? If it is true that this idea includes the Devil
speaking 'unknown' languages, does that mean that he can speak them
without prior knowledge or that the languages are only unknown (or
unknowable) to us?

Most of the stuff I came up with through Google searches had to do
with speaking in tongues, or glossalia. I am not interested in the
origins of this phenomenon, except as it could be related to my main
question.

Satan was once a powerful angel and as such he logically possesses the
capabilities of an angel. The Bible says that angels have their own
language:

1Cr 13:1 Though I speak with the tongues of men and of angels, and
have not charity, I am become [as] sounding brass, or a tinkling
cymbal.

Dionysius wrote:

"They [the angels] need neither tongue nor ears but with-out the help
of any spoken word they exchange with each other their thoughts and
their counsels. This form of expression, the angelic language, may
seem perhaps too faint and indistinct to us who are used to material
sound and words of mouth; it is however much stronger, clearer, and
more perfect than any human language, even when this is used by the
most learned and experienced of men. Our words of mouth are no more
than symbols of the ideas we have in our mind and wish to manifest to
others. Symbols and words are very often inadequate in expressing the
full thought, or they are ambiguous or not well understood by the
hearer. To be able to open one's mind and reveal the whole thought, as
it is there, without the channel of symbolism, sound, and words, is a
higher and better form of expression. Such is the wordless exchange of
ideas, the language of the angels.?

For what it?s worth;
Tutuzdad-ga

When God commenced creation, Jesus was first. He was a master worker
beside God [Proverbs 8;22] Satan was created an angel who, by misusing
his gift of free will, challenged God`s right to dictate good
behaviour. Satan therefore was present when all the world was one
language [Genesis 11;1]. Verse 4 says that people planned to build a
tower [ The tower of Babel] to celebrate just how good they were. They
failed to give credit to God for their existence. So, in verse 7, it
states that God confused their languages and they were no longer able
to communicate, and so the building work ceased and the people
scattered over the earth. Verse 9 names the city as Babel. We, even
today, in english, use the word babble to mean meaningless chatter.
Nothing can be organised with it. So whatever languages were in
existence then and any since, would all have to be well known to
Satan.

I have done tons of research on the old fella "Satan" and I can't say
that I have come across any scripture that says anything about him and
talking in unknown languages, but if you follow the "mythology" set
forth, then something like speaking an "unknown" or in the case of the
Exocist a "dead" language like Latin is not really a big deal. I also
don't mean to ofend anyone by using the term "mythology", but a
scholarly study of "Satan" reveals a long evolution of ideas and
concepts that have evolved into the image we have today. A lot of what
we think of about Satan today is what biblical scholars term
"secondary traditions" meaning they came about at a later date (
typically the middle ages) and over time became thought of as true
scripture. Dante's Inferno highly influenced these images, as well as
prominent church leaders of the time like Clement of Alexander (
150-213 CE), Saint Augustine (354-430 CE), and of course Thomas
Aquinas (1225-1274).
  I think the online Catholic Encyclopedia said it best:

"Mention is made of the Devil in many passages of the Old and New
Testaments, but there is no full account given in any one place, and
the Scripture teaching on this topic can only be ascertained by
combining a number of scattered notices from Genesis to Apocalypse,
and reading them in the light of patristic and theological tradition."

http://www.newadvent.org/cathen/04764a.htm

The key phrase there is the last line, which basically says "there are
all kinds of passages that we have gone back and attached to Satan,
but really aren't about him"....These include the name Lucifer, the
devil as the serpent in Eden, and many others.

The online Catholic Encyclopedia ( powered by Google) is an excellent
place to get information on religious subjects. Yes it is the Catholic
point of view, but since they created some of the most influencial
interpretations of scripture, it is a great starting place to see how
the ideas were conceived.


Below is an excellent link to start with that gives a great overview
of Satan, including a chronology of how he evolved from ancient Israel
up to 100 C.E.(old testament writings),and then 100 C.E. to present
times. It is fascinating reading, and I promise will shed a lot of
light on how things developed to what we think of today. There is also
a section that discusses powers and abilities usually attributed to
Satan.

http://www.religioustolerance.org/chr_sat1.htm

Enjoy, and you have touched on an amazing biblical subject that is
quite rewarding to research.

Jeff