Luke 6:16

‘And Judas the son of James, and Judas Iscariot, who became a traitor.'

Judas, the son of James (‘Judas, not Iscariot' - John 14:22), is probably Thaddaeus, (which Matthew possibly has as Lebbaeus. This is, however, by no means certain as many manuscripts have Thaddaeus. One may have been a new name and one a nickname). Judas Iscariot is always mentioned last because he betrayed Jesus. Luke specifically designates him as the one who became a traitor. If his name means man (ish) of Kerioth (which is by no means certain), he was the only Judean among the Apostles. It may, however, be that his name is derived from the Aramaic word seqar, ‘falsehood', with a prosthetic aleph added.