Historically, people groups could be classified by the patriarch or matriarch (the starting bloodline), by region they lived in (often named after prominent ancestors), or by the language they spoke. As stated in the Bible, there were 2 early timespans in mankind's history that allow us to trace a portion of our lineage - prior to the global Flood and after the Flood.
The Bible not only states the 12 Tribes (sons) of Israel (Jacob) and the Jews (from the specific family line of Judah), but also chronicles the history of mankind.
Pre-Flood lineage (Adam to Noah) - Genesis 5
Some Arabs descend from Keturah (Abraham's 2nd wife), Moses' 2 sons, and potentially earlier people who exited Noah's Ark.
Noah's Ark rested in modern-day Turkey near the Armenian & Iranian borders. The earliest civilizations include those from Mesopotamia (Akkadians, Sumerians, Assyrians and Chaldeans such as the Babylonians) and shortly thereafter in Africa (Egyptians). After the Flood, mankind spread across the globe from those regions. As a generalization, Japheth's offspring mostly moved into Europe but also spread into North Africa. The Greeks and Romans came from Japheth's line (through Javan) after his descendants began exploring the Meditteranean Sea. The early Indus Valley occupants appear to be descendants of Madai, a son of Japheth. Ham's offspring seemed to dominate both in Mesopotamia & the African continent. Shem's line mostly remained in the Middle East and Asia. Considering the geographic regions these family lines appear in, Asians like the Chinese could easily be considered either Semitic in origin or also from Japheth's line; but, other evidence links them with the Hittites or Sinites, making them Hamites.
Of the 3 sons of Noah, 2 created regionally dominant languages.
Arameans (possibly the original language) - spoke and wrote Aramaic from the line of Aram; official language of the Assyrian & Persian empires; today, Kurds still speak Aramaic or at least a form of Aramaic
Hebrews - Israelites & Jews spoke and wrote Hebrew; after the Tower of Babel incident, different languages developed as people began spreading throughout the lands
Greeks - Macedonians and others who lived in the region of what is now known as Greece; probably from Javan's portion of the family line after the Flood
Latins - Romans developed this language which served as the basis for other languages such as Cyrillic
Keep in mind that sometimes people groups can identify the same people but have different names by various ethnic groups. For a more recent example, people and places in the colonial United States sometimes had 3 different names to each of the Native Americans, French & English.
Initially, names identified bloodlines and professions. Just as Smith is a very common name for silversmiths, blacksmiths or other tradesmen, males were identified as sons of certain historical figures as well as the locations where they lived. Jesus of Nazareth and James and John, sons of Zebedee are examples of this. Mary, mother of Jesus, is another example. As mankind grew, people often were named after their ancestors which mandated a way to distinguish between people who, in this case, aren't alive to tell their stories. King Saul in the Old Testament isn't the same Biblical character as Saul that became the apostle Paul. There are also at least 3 women named Mary named in the Bible: Mary Magdalene, the virgin mother Mary, & Mary, the sister to Martha.
In some cases, the same people have names in different languages such as the prophet Daniel. In Hebrew, he was known as Daniel while the Babylonians named him Belteshazzar. Read Daniel 1 for the story of Daniel.
Between translations people sometimes have slightly differing spellings, but may sound similar when spoken. Translators did their best to maintain accuracy of the historic manuscripts.