disconcert
UK: ˌdɪskənˈsɜːt | US: ˌdɪskənˈsɜːrt
vt. to disturb the composure of; unsettle
vt. to frustrate or thwart (plans, expectations)
The word "disconcert" combines the prefix "dis-" (indicating reversal or negation) with "concert" (from Latin concertare, meaning "to harmonize"). Originally, "concert" referred to mutual agreement or harmony. By adding "dis-," the term evolved to signify disruption of harmony or composure, first appearing in English in the 17th century to describe emotional or situational unsettlement.
His sudden outburst disconcerted the entire audience.
The unexpected question disconcerted her during the interview.
Changes in the schedule disconcerted our carefully laid plans.
She remained calm, refusing to let criticism disconcert her.
The eerie silence in the house disconcerted the visitors.