English term (edited): privileged and confidential

There is no need to put the phrase in quotes.

These are two terms, but can be allowed here because they often occur together, and they are often confused, so it helps to disambiguate them.

1. Privileged: This term means that the material enjoys a privilege. The privilege hinted at here is the attorney-client privilege, which prohibits even the court or law enforcement officers from having access to the material. This particular privilege is called حصانة الوكلاء والموكلين

Material that enjoys this privilege is referred to as مواد متمتعة بالحصانة

Just as in English, the nature of the حصانة is understood. There is no need to name it explicitly.

2. Confidential: This term means that the material is being shown to someone "in confidence." That means that the attorney is relying on his/her trust in this person not to show it to anybody else. This act of trusting is called ائتمان

The material itself is called مادة مؤتمنة