Recognizing that "Gentile" simply means "not quite like us" Mormons call non-Mormons "Gentiles" and Jews call non-Jews "Gentiles". But outside a specific context the word Gentile does not stand on it's own.
For Example: The Lost Sheep of the House of Israel are a unique sub-set of Gentiles who are Israelites, but not Jews. From a Jewish perspective they are Gentiles, but from an Israelite perspective they are not. So when we read:
Matthew 10:5-6 These twelve Jesus sent out and commanded them, saying: "Do not go into the way of the Gentiles , and do not enter a city of the Samaritans . But go rather to the Lost Sheep of The House of Israel."
we need to remember that the Title House of Israel was assigned to the Northern Kingdom as part of their Eternal Heritage when the Davidic Kingdom split. Its members were never Jewish, therefore Jesus command to go first to the Lost Sheep of The House of Israel was NOT a command to go first to lost Jews.
Jesus was both an Israelite and a Jew and what He said here was "do not go to the Israelite Gentiles." (A common misinterpretation has Him talking about Jewish Gentiles .)
The House of Israel later became The Lost Tribes of Israel who won their freedom from the Assyrians ~610 BC. These 5 MILLION Israelites spread quickly to the West and North where they became known to history as The CELTS and later as The Europeans and Americans. It was to these non-Jewish ISRAELITE CELTIC GENTILES in Galatia , etc. that Jesus first sent his 12 apostles.
These Northern Kingdom Israelites were not Jews, thus were Gentiles in the Jewish sense. But they were not Gentiles in the Israelite sense because they WERE Israelites. This huge nation of Israelites was simply called the The Lost Sheep of the House of Israel .
These ISRAELITE CELTIC GENTILES made up the bulk of the early Christians, and all the promises they received as Israelites were, and are, still good today. Gods inheritance has no statue of limitations.
Is the Israel-Celt connection the reason that Irish Gaelic and Hebrew sound so similar? I was shocked the first time I heard someone speaking Gaelic on an audio tape my daughter had. I thought the language learning company had packed a Hebrew tape in the box by mistake.