Do Jehovah's Witnesses use different language for theological reasons? They don't have churches: they have Kingdom Halls (though it's not wrong to refer to a Kingdom Hall as a type of church).

They don't have hymns: they have Kingdom Songs (though it's not wrong to refer to a Kingdom Song as a hymn).

They don't have priests; they have elders (maybe this one is more understandable: they're not alone in having elders, and not having priests is a theological point).

They divide the Bible into the "Hebrew (and Aramaic) Scriptures" and the "Christian Greek Scriptures" (not just the "Greek Scriptures", to prevent possible confusion with the Septuagint).

Are any of these differences actually theologically meaningful?
I can't verify the accuracy of this post, but the origin of "Kingdom Hall" is given here (and I would imagine that the phrase "Kingdom Songs" has a similar origin). 


  The name Kingdom Hall was suggested in 1935 by J. F. Rutherford, who
  was then president of the Watch Tower Society. In connection with the
  Society's branch facilities in Honolulu, Hawaii, [...] When James
  Harrub asked what Brother Rutherford was going to call the building,
  he replied: "Don't you think we should call it 'Kingdom Hall,' since
  that is what we are doing, preaching the good news of the Kingdom?"
  Thereafter, where possible, halls regularly being used by the
  Witnesses gradually began to be identified by signs that said "Kingdom
  Hall." -- Proclaimers Chap 20, p. 319


As to the "Hebrew (and Aramaic) Scriptures" and the "Christian Greek Scriptures" , again, I'm not sure of the accuracy of the Wikipedia article I'm about to quote, but the citations point to the original Watchtower publication.

Wikipedia offers this:


  The translators use the terms "Hebrew-Aramaic Scriptures" and
  "Christian Greek Scriptures" rather than "Old Testament" and "New
  Testament", stating that the use of "testament" was based on a
  misunderstanding of 2 Corinthians 3:14.[29] When referring to dates in
  the supplemental material, the abbreviations "B.C.E." (Before the
  Common Era) and "C.E." (Common Era) are used rather than BC and AD.


You've already answered the question of "Elders" yourself.