If you say that someone is nervy, you mean that their behaviour is bold or daring. John liked him because he was a nervy guy and would go out and shoot anybody who John wanted him to shoot
showing or requiring courage and contempt of danger; "the nervy feats of mountaineers
If someone is nervy, their behaviour shows that they are very tense or anxious, or they are the type of person who is easily upset. Alan was irritable, and very evidently in a nervy state. = jumpy
showing or requiring courage and contempt of danger; "the nervy feats of mountaineers"
offensively bold; "a brash newcomer disputed the age-old rules for admission to the club"; "a nervy thing to say"