“Jew” comes from “Judah,” (meaning praise)

Romans 2:17 KJV

Behold, thou art called a Jew, and rests in the law, and makes thy boast of God,"

Previously called Hebrews and Israelites, by the first century.

Just reminding you that one of the tribes (sons), of the 12 tribes of Israel was Judah (“Jew”).

Because Gods chosen people, by constantly disobeying, were dispersed into other countries.

Babylonian Empire/Medo-Persian Empire.

By the time they were allowed to return 

(By Gods intervention), 

they trickled down into one!

God knows that you know how 

'human trickle down works’.

http://www.logicandlight.org/busted-1-synagogues-didnt-exist-in-jesus-time/

“Jew”

 had become the most common name for the descendants of Abraham through Isaac.

“Jew” comes from “Judah,” (meaning praise),

one of the twelve tribes and the designation for the southern half of Solomon’s kingdom after his death.

From the time of the Babylonian captivity, the whole race bore this title.

Their great heritage, however,

became a source of pride and complacency which led to judgment instead of praise.

The Jews knew they were God’s chosen.

They were proud, but they looked down on those who were not Jews

thinking themselves better than others.

Paul is telling them here that it is wrong to depend on the fact of their Jewish heritage to save them.

The Babylonians were conquered by Persia about 540 B.C.

Babylonia and the Hebrew Kingdoms of the Old Testament.

Babylonia was an important, but integral, part of the Assyrian Empire

until it rose in rebellion in 626 B.C. under Nabopolassar and his son, Nebuchadnezzar.

By the time it became an empire, the Northern Kingdom (Israel) was gone.