An early group of people mentioned only twice in the Old Testament (Genesis 6:4; Numbers 13:33). The Greek translation of the Hebrew Scriptures (the Septuagint) translated "Nephilim" as "giants." Other versions, like the King James Version, followed this. Most modern translations call them Nephilim. They link them to the Anakim (Numbers 13:33; Deuteronomy 2:21) and the Rephaim (Deuteronomy 2:20). These groups were known for their large size, which is why they were often called "giants."
The origin of the Nephilim is unclear. Some say the Hebrew verb naphal, meaning "to fall," implies the Nephilim were "fallen ones." These were fallen angels who later had children with human women. But Jesus taught that angels do not have physical relationships (Luke 20:34–35). This idea assumes that Genesis 6:1–4 reflects Greek myths, where such unions happened. However, the passage in Genesis is about human history, not mythology.
The Nephilim were probably not the "sons of God" in the Bible. They seem different from the "daughters of men." To understand them, think of an ancient people group, like the Anakim and Rephaim, whose origins are unknown.