unnerve
un-NURVverbMeaning to make someone lose courage or calm
Memory hook UN-NERVE: his NERVE is gone. Dev boasted he would jump from the high rock into the river, but standing at the edge, he loses his nerve. The height unnerves him.
The creaking floorboards unnerved the new babysitter.
In context The goalie was usually steady, but the roaring crowd unnerved him; his hands shook, and he let in two easy goals.
Similar rattle, unsettle, frighten, fluster
Opposite reassure, steady, calm
From un- (taking away) + nerve, in its old sense of strength and courage.