ANSWER:
Let me explain to you, briefly. Yisroel was a name, a generic name, given to denote the superiority of the Am Yisroel. They are going to conquer with the help of Hashem, Yisro - keil they are going to conquer with the help of Hashem. And that's the name to this day.
However, among the tribes of Yisroel there was one that remained most loyal. The sons of Yosef did not remain most loyal. Ephrayim and Menashe broke away. Yerovom ben Nevot from shevet Ephrayim broke away, and he lost contact with the Beis Hamikdash, and he went into devious paths that bordered on idolatry, and finally they went lost among the nations.
But Yehuda (ויהודה עד רד עם אל (הושע יב.א, Yehuda was still clinging to Hashem. It's because of the influence of Dovid of Yehuda. Dovid's heart was most loyal, בעבור דוד עבדי, My servant Dovid. And therefore because the Yehudim were the ones who clung to Hakadosh Baruch Hu despite everything, that's why today we are called Yehudim.
It's not enough to choose virtue and to make a Kabolas Hatorah, and to become great; it's essential to stick to it, על אבותינו ועלינו,על בנינו ועל דורותינו, all the generations. But there came a time when they fell down on the job, and therefore they were rejected, they were lost, ואבדתם בגוים, they were lost among the nations.
But Yehuda remained till this day, and now we are called Yehudim.
Good Shabbos To All
This is transcribed from questions that were posed to Harav Miller by the audience at the Thursday night lectures.
To listen to the audio of this Q & A please dial: 201-676-3210