This apostle is harder to name than most. The lists of Matthew and Mark include a Thaddaeus (some manuscripts, Lebbaeus), while Luke and Acts instead list a Judas of James, usually rendered Judas the son, or brother, of James. The church early identified the two, producing the composite Jude Thaddaeus and taking pains to keep him clear of Judas Iscariot, the betrayer. The Gospel of John marks the distinction explicitly when Judas, not Iscariot asks Jesus a question at the last supper, the one saying attributed to him in the Gospels.
Tradition also made him the author of the short Epistle of Jude near the end of the New Testament, whose writer calls himself Jude, a servant of Jesus Christ and brother of James. Most scholars doubt the apostle wrote it: its polished Greek, its use of Jewish apocryphal works such as 1 Enoch, and its reference to the apostles as figures of the past point to a later hand, and the brother of James it names is more plausibly James the brother of the Lord than a member of the twelve.
As so often with the lesser apostles, the New Testament offers a name, a single question, and then silence, into which the later church poured a remarkable devotion.