Boyd’s Bible Dictionary:

Contraction of Judah
Man of Judea (2 Kings 16:6; 25:25). After captivity, Hebrews in general (Ezra 4:12; Dan. 3:8-12). Antithesis of Christian in N. T. (John; Rom. 1:16).

Concise Bible Dictionary:

A man of Judah. The term does not occur until after the division of the kingdom (2 Kings 16:6; 2 Kings 25:25). It is applied to any one belonging to the two tribes, and it may have been used respecting any of the ten tribes who remained in the land at the captivity or returned thither. The name is principally found in the Old Testament in Ezra, Nehemiah, Esther, and Jeremiah. In Esther the name is applied to all the Hebrews in Persia. In the New Testament the name occurs most frequently in the gospel of John, where it is applied to those of Jerusalem and Judaea in distinction from “the people” who may have been Galileans or visitors from a distance. John speaks of “the Jews,” “the Jews’ passover,” and so forth, as though he were not a Jew. They had rejected the Lord, and in spirit John was separate from them.
In the addresses to the seven churches we twice read of those who “say they are Jews, and are not.” The name is there used of those claiming to be the people of God by descent, but not so morally, as in another place there are some “who say they are apostles, and are not” (Rev. 2:2,9; Rev. 3:9). In a similar way the Jews prided themselves in being “sons of Abraham,” whereas, the Lord declared that they were not such morally. The name JEWESS occurs only in Acts 16:1 and Acts 24:24.

Jackson’s Dictionary of Scripture Proper Names:

same as Jehudi