The word Gentile (or its plural) is found 131 times in the KJV Bible. The book of Acts contains the most occurrences with 30 followed by Romans with 24. In the Old Testament, it is derived from the Hebrew Goy (Strong's #H1471) which means a nation or people that are not Israelites.
In the New Testament, the singular word Gentile comes from Hellen (Strong's #G1672) which references a Greek-speaking person. The plural of the word comes from ethnos (Strong's #G1484) which is a race or group of people that are non-Israelites.
The Bible additionally uses several synonyms for Gentiles. Many times such people, in the Old Testament, are called strangers (Exodus 12:49, Leviticus 19:33 - 34) or heathen (Leviticus 25:44, 26:45). The New Testament calls them Greeks (Romans 1:16). The terms "nations," "uncircumcision" and "uncircumcised," found in both Testaments, are also a synonym for a Gentile.
By these were the isles of the Gentiles divided in their lands; every one after his tongue, after their families, in their nations. (Genesis 10:5, KJV).
And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed. (Galatians 3:8, KJV).
And when a stranger shall sojourn with thee, and will keep the passover to the Lord, let all his males be circumcised, and then let him come near and keep it; and he shall be as one that is born in the land: for no uncircumcised person shall eat thereof. (Exodus 12:48, KJV).
Therefore if the uncircumcision keep the righteousness of the law, shall not his uncircumcision be counted for circumcision? (Romans 2:26, KJV).
Change in Usage
God considered the entire nation of Israel, all thirteen tribes, as being his chosen and holy people (Deuteronomy 7:6, Psalm 135:4, Isaiah 41:8). All those who were not Israelites were called strangers or heathen.
Unfortunately, especially in modern times, the word Gentile is erroneously used to refer to anyone who is not Jewish instead of someone who is not an Israelite. This is partly due to the Jews not losing their identity when they went into Babylonian captivity from 605 to 586 B.C. Jews represents only three of Israel's thirteen tribes!
Israel's ten "lost tribes" were known to exist in the first century (James 1:1), a vast number of their descendants live today, and they will be among the many called to repent during the Great Tribulation (Revelation 7). They are also "God's chosen people" even though they are erroneously labeled (or think of themselves as) Gentiles!
Did You Know . . .
Under rabbinic law, a Gentile is only required to observe the Seven Laws of Noah (the Noahide or Noachian laws) while Jews must observe the laws of Moses. These Noahide laws are not to worship idols, not to curse God, not to commit sexual immorality or adultery, not to commit murder, not to steal, not to eat the flesh torn from a living animal and the establishment of courts of justice.
Four women in Jesus' legal lineage back to King David and Abraham, through his stepfather Joseph, were Gentiles. They were Tamar (wife of Judah, Matthew 1:3), Rahab (Matthew 1:5), Ruth the Moabitess (Ruth 4, Matthew 1:5) and Bathsheba (Matthew 1:6).
New Testament Famous
Infamous New Testament non-Israelites include Herod the Great (an Edomite), Herod's descendants (Herod Agrippa I, etc.) and Pontius Pilate. Others include Alexander the Coppersmith (vehemently opposed Paul), Felix and Festus (Roman Procurators) and more.
Famous "good" Gentiles include the Magi (high-level Parthian priests), Cornelius (first recorded non-Jew to become a Christian), Dionysius and Damaris (Athenian converts), and Julius (Roman Centurion who treated Paul kindly).
The Apostle Paul's ministry centered on preaching the gospel to Gentiles (Acts 9:15, Romans 15:16, Galatians 2:8, 2Timothy 1:11). In fact, eleven of his fourteen books were written to audiences primarily composed of non-Israelites. His close friend Timothy had a non-Israelite father and Luke, who wrote one of the gospels and traveled with him, was a Gentile convert to Christianity.