Janna = "he vexed"
1) he and Jambres, were two Egyptian magicians who in the presence of Pharaoh imitated the miracles of Aaron in order to destroy his influence with the king. The author of the epistle derived their names from the tradition of the Talmudists and the Rabbins
Part of Speech: noun proper masculine
Citing in TDNT: 3:192, 344
Of Egyptian origin; Jannes, an Egyptian: - Jannes.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root Ἰάννης; click on the second column to search for that grammatical form of the root Ἰάννης; click on the third column to search for that word and grammatical form; click on the total to search for the root Ἰάννης.