Disconcert (verb)

1. To disturb the composure of someone; to unsettle or confuse someone.
2. To cause someone to feel uneasy or awkward.

Origin:

From french 'désconcerter', from 'dis-' meaning 'not' and 'concerter' meaning 'to concert'.

Examples:

1. The sudden noise disconcerted the speaker and he lost his train of thought.
2. The unexpected news disconcerted her.
3. The unfamiliar surroundings disconcerted the tourists.
4. His lack of response disconcerted her.
5. The sudden change in plans disconcerted the team.