The enigmatic "Nephilim" of (Genesis 6:4) get names in Targum Pseudo-Jonathan. "Schamchazai and Uzziel, who fell from heaven, were on the earth in those days."
These are the Watchers — the angels who descended to earth in the ancient Jewish tradition preserved in 1 Enoch (3rd-2nd centuries BCE) and the Book of Jubilees. Shamchazai (sometimes Shemhazai) and Uzziel (or Azazel) led a band of angels who left heaven, took human wives, and fathered giants. The Targumist condenses this entire mythic tradition into a single verse.
What "fell from heaven" means in Jewish thought
It is crucial to understand this in Jewish terms, not in any other. These Watchers did not rebel against God the way later traditions imagine. They descended — left their post, crossed a boundary they should not have crossed, but they were not at war with the Creator. They were angels who lost their discipline. The Nephilim are their children, the fallen giants.
"After the sons of the Great had gone in with the daughters of men, they bare to them: and these are they who are called men who are of the world, men of names."
"Men of names" — anshei ha-shem — the legendary heroes of the ancient world. The Targumist preserves the ambiguity. These were celebrated figures. Great men, mighty men. But their greatness came from a union that should never have happened. Their fame is real; their origin is corrupt. The Flood will wash them away.