Greek Ioudas (the same form as Judas — he identifies himself in his epistle as "Jude, a servant of Jesus Christ and brother of James," deliberately distinguishing himself from Judas Iscariot). One of the half-brothers of Jesus (Matthew 13:55, Mark 6:3), son of Mary and Joseph, brother of James the Just. Like his brother James, Jude did not believe in Jesus during the earthly ministry but became a believer after the resurrection. Author of the short epistle that bears his name, one of the last NT books chronologically.
The epistle of Jude is 25 verses of red-alert theology. Jude explains at the outset that he had intended to write about "our common salvation" but felt compelled to write instead to urge believers to "contend for the faith that was once for all delivered to the saints" (v. 3) because false teachers had "crept in unnoticed" (v. 4). The bulk of the letter is a vivid denunciation of these infiltrators — comparing them to the Sodomites, to Cain, to Balaam, to Korah, calling them "waterless clouds... fruitless trees in late autumn... wild waves of the sea... wandering stars" (vv. 12-13). He quotes the apocryphal book of 1 Enoch (v. 14-15) in a way that illustrates that citing extrabiblical sources as illustrations does not canonize them (Paul does the same with Greek poets in Acts 17 and Titus 1:12). The letter ends with one of the most beloved doxologies in the NT: "Now to Him who is able to keep you from stumbling and to present you blameless before the presence of His glory with great joy, to the only God, our Savior, through Jesus Christ our Lord, be glory, majesty, dominion, and authority, before all time and now and forever. Amen" (vv. 24-25). Jude is essential reading whenever deceivers infiltrate the Church. Every generation needs its Jude.