Reticence (noun)

1. The tendency to be silent or not to speak freely about one's thoughts, feelings, or experiences.
2. The tendency to be reserved or uncommunicative.

Origin:

From the latin word "reticentia" meaning "silence" or "restraint".

Examples:

1. The detective noted the suspect's reticence during the questioning.
2. The employee's reticence made it difficult for the manager to understand her concerns.
3. The politician's reticence on the issue raised questions about his stance.
4. The student's reticence in class made it difficult for the teacher to gauge her understanding.
5. The witness's reticence made it difficult for the lawyer to establish the truth.