Always applied in the gospels to Judas who betrayed Jesus to distinguish him from another Judas among the apostles. Iscariot may mean ‘man from Kerioth’; or there is a suggestion in one ancient MS which connects it with the Latin sicarius, which could imply that Judas was one of the dagger-men, that is the Zealots, as they were later known, nationalists who favoured armed rebellion against the Romans. See judas 4.