As is natural in all subcultures, Christians have developed dialects. Christians (Protestants and Catholics, clergy and laymen) use many terms non-Christians would not understand. Well, perhaps more often than not outsiders understand us—but we simply look odd. One of the biggest grievances against Christian culture is our bubble-like tendency. We can genuinely hurt the cause of Christ when we create holy huddles, only experiencing the world through our own eyes or the eyes of other Christians.
I've heard many people refer to this phenomenon as "speaking Christianese."