Angel names

Metatron, Sandalphon, Akatriel - these are the names of high-level angels.  Metatron is the Prince of the Countenance, God's right-hand man and scribe.  Sandalphon stands behind the Divine Throne, taking our prayers and weaving them into crowns, to be passed to the Divine.  Akatriel sounds like Sandalphon's function (I will crown God), but is also taken as a God-name.

What differentiates the first two from the last name?  The first two sound Greek, while the last is clearly Jewish.  The most common name-form for angels in Hebrew mythology is a Hebrew word or expression suffixed with -el or -iel.  E.g. Michael -who is like El?  Gabriel- strength of El. Etc., where El is a God-name.

Metatron is one of the more interesting myths.  Enoch, who lived between Adam and Noah, is not listed as dying in the Begats list.  Rather, he "walked with God".  This anomaly is the basis of the Enoch myth, where Enoch is taken up bodily into Heaven, much like Elijah was centuries later, and is transformed into the chief angel, Metatron.

However, in early apocalyptic literature, Metatron is known under different names, more like the standard theophoric angel names: Yahoel (a combination of the God-names Yaho and El), or Hashem Katan, the small God.  By the time of the Tannaim, though, he is known as Metatron (which sounds like a Japanese robot name, like Voltron; or a 1950s computer, like Datatron).  Sandalphon (which sounds like the late-antiquity version of the Sports Illustrated Sneakerphone[TM]) only appears in the Tannaitic period.

Which leaves me wondering, why the sudden shift to Greek names for the highest-level angels?  Had the names become so holy that they needed kinnuyim (euphemisms)?  Even today, many religious Jews won't even pronounce the Greek angel names, preferring an abbreviation such as "the angel Mitat" for Metatron.  Did a new growth in metaphysical speculation engender a shift to exotic foreign cognomens?

Further, what do the names mean?  The articles below offer a variety of suggested etymologies for Metat and Sandal, but generally leave them as "we don't really know".  I checked out Metatron (with a couple of possible spellings) on Google Translate, and they translate the word as "conversion" or "converted".  I wonder if it could be that simple - Enoch was converted into Jahoel/Metatron - so his name could be "the converted one".

Sources:
http://www.jewishencyclopedia.com/articles/13172-sandalfon
http://www.jewishencyclopedia.com/articles/10736-metatron
http://en.wikipedia.org/wiki/Metatron
Gershom Scholem, "Jewish Gnosticism and Merkabah Mysticism", JTSA 1965.