Is there a difference between nephilim and rephaim?

Dr. Tony Mariot is a Freelance Research Writer Biblical Antiquity at University of Oxford

The Rephaim are known from biblical, Ugaritic, and Phoenician sources. In the Bible two uses of the term are discernible.

The first is as a gentilic (e.g., Gen. 14:5; 15:20; Deut. 2:11) referring to a people distinguished by their enormous stature.

Especially singled out is Og king of Bashan (Deut. 3:11) and the adversaries of David (II Sam. 21:16, 18, 20).

The bottom line is there is no difference

Genesis 6:4

4 There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.