Giants are first mention in the Word in Gen.6:4 with an explanation of how they came to be.
It is an important note in Matt.24, Mark 13, and Luke 21 of end time activities, that are the mile-marker: wickedness of intermarriage with fallen angels. Lots of violence, corruption; "their thoughts and imagination was evil, continuously" - anything goes. The flood wiped them out.
In Num.13:28-33 there is another influx of Giants: Dr. Bullinger refers to this as "Irruption." They are referred to as "children of Anak." These Giants were "great" in size as well as wickedness. They were self titled as champions, because of their violence and fighting skills.
Deut. 2:11, 2:20, 3:11, 3:13 Mentions a history of Giants. Jos.12:4, 13:12, 15:8, 17:15, 18:16 - Giants that had to be dealt with in the promised land.
2Sam21:16, 21:18, 21:20, 21:22 all mention Giants. We see David showing us how to take them out. His brothers took out four of Goliaths brothers.
Giants aka Nephilim are a result of fallen angels marriage to women, producing Giants. These angels are dead-spirits-talking, because their Judgement has been pronounced = totally destroyed the moment Immanuel-Christ-Jesus returns.
Nephilim/Giants are wicked and rebellious because they followed Satan in It's attempt to overthrow Heaven. They illegally came to earth without being born of woman. Whatsoever they produce - will be wicked as well. Soon, another "Irruption" will occur.
1Cor.11:5 is in play. The Covering is Christ's Spirit = the Holy Spirit: to stop the climax of wickedness from taking place.