Jargon

Why do we use jargon? Why not just use "ordinary" language? Did the Apostles or Jesus Christ use jargon? I believe the answers to all these questions are important and say something about the way we use language.
First, by jargon I mean a word or set of words which have a specific meaning to one group of people and which may be incomprehensible or do not convey the same meaning to others. In the Philadelphia Story, Tracy calls the "True Love" a "yar" boat. For most people who have never seen the movie the word "yar" conveys little, if any, meaning and so it can be considered jargon.
Second, we use jargon because it is a shorthand method of saying something. "Yar" for example means something like, handles well, is trim, looks good, is a great boat and so on. Theologians have their own jargon. Apologetics, for example means "the science of attempting to explain or persuade someone who doesn't hold to Christian beliefs the reasonableness of the Christian faith."
Third, jargon is useful in situations where the meaning of each term is clear for saying a lot without having to spell out the meaning each time. In a group of Reformed theologians, for example, one would imagine that it would be appropriate to use the mnemonic TULIP for those characteristic beliefs of Calvinism (and yes, Reformed and Calvinism are themselves jargon terms). The qualifier is important because the purpose of language is to communicate ideas from one person to another. If the receiver doesn't know what you are talking about you have failed to communicate. Like all shortcuts the saving comes at a price, an increase in possible misunderstandings.
Fourth, Did the Apostles and the Lord Jesus Christ use jargon? Yes, at times. When the Lord Jesus was talking to the Jewish leaders of the day he said they should know "the Law and the Prophets." This was a shorthand way of saying they should know their Bible - entitled the Law, the Prophets and the Writings (in the Hebrew language, of course). Another time he spoke of John the Baptist and said: I tell you Elijah has come and a greater than Elijah is here ... the significant of which requires an awareness of a prophecy in the Old Testament.
So, what about us? I believe it is important at times to be aware of when jargon is appropriate or inappropriate and adjust our language accordingly. Inappropriate use of jargon is a quick way to have your hearers decide you are not worth listening to. If in doubt, spend the extra words.