Easton's Bible Dictionary

Thaddaeus - breast, the name of one of the apostles (Mark 3:18), called "Lebbaeus" in Matt. 10:3, and in Luke 6:16, "Judas the brother of James;" while John (14:22), probably referring to the same person, speaks of "Judas, not Iscariot." These different names all designate the same person, viz., Jude or Judas, the author of the epistle.