That "Jews" refer only to the descendants of Judah is not ringing true to this Bible student. Would love to hear a studied opinion on the topic. This may be a worldly understanding or usage of "Jew", but I doubt it is the Biblical one. As an example, am thinking of "Israel" usage as well. God first intro'd the word "Israel" for Jacob after he wrestled with the Angel of the LORD. After the Exodus & resettlement in the Land, all 12 tribes formed the nation of "Israel". Later, ten tribes split off to form Israel in the north, leaving two tribes in the south which were referred to as "Judah". The regathered, reconstituted nation of Jewish descendants in the Land today is called "Israel". So the word "Israel" is in the same "confusion". Maybe it's best not to split hairs over this, but to leave it open to "experts" to study. See "Israelites" in Wikipedia, which may or may not be fully accurate.