Here is some information from Easton's Bible Dictionary:
Gehazi: valley of vision, Elisha's trusted servant (2 Kings 4:31; 5:25; 8:4,5). He appears in connection with the history of the Shunammite (2 Kings 4:14,31) and of Naaman the Syrian. On this latter occasion he was guilty of duplicity and dishonesty of conduct, causing Elisha to denounce his crime with righteous sternness, and pass on him the terrible doom that the leprosy of Naaman would cleave to him and his for ever (2 Kings 5:20-27). He afterwards appeared before king Joram, to whom he recounted the great deeds of his master (2 Kings 8:1-6).