Diffident (adjective)

1. Lacking confidence in one's own abilities, worth, or fitness; timid.
2. Hesitant to draw attention to oneself; reserved.

Origin:

From latin diffidens, meaning "lack of trust".

Examples:

1. He was diffident about his chances of winning the competition.
2. She was diffident about speaking in public.
3. The diffident employee was reluctant to share his ideas in the meeting.
4. His diffident demeanor made it hard for him to make friends.
5. The diffident student needed encouragement to speak up in class.