Jehovah Nissi, The Lord Is My Refuge, Banner.

Use in the Bible: In the Old Testament Jehovah-Nissi occurs only once in Exodus 17:15.

Jehovah Nissi in the Septuagint: kurios kataphugê mou…the Lord is my refuge (banner)

Meaning and Derivation: Jehovah is translated as "The Existing One" or "Lord." The chief meaning of Jehovah is derived from the Hebrew word Havah meaning "to be" or "to exist." It also suggests "to become" or specifically "to become known"…this denotes a God who reveals Himself unceasingly. Nes (nês), from which Nissi derived, means "banner" in Hebrew. In Exodus 17:15, Moses, recognizing that the Lord was Israel's banner under which they defeated the Amalekites, builds an altar named Jehovah-Nissi (the Lord our Banner). Nes is sometimes translated as a pole with an insignia attached. In battle opposing nations would fly their own flag on a pole at each of their respective front lines. This was to give their soldiers a feeling of hope and a focal point. This is what God is to us: a banner of encouragement to give us hope and a focal point.

Commentary:
Moses took care that God should have the glory of it instead of setting up a triumphal arch, to the honour of Joshua (though it had been a laudable policy to put marks of honour upon him), he builds an altar to the honour of God, and we may suppose it was not an altar without sacrifice but that which is most carefully recorded is the inscription upon the altar, Jehovah-Nissi--The Lord is my banner, which probably refers to the lifting up of the rod of God as a banner in this action. The presence and power of Jehovah were the banner under which they enlisted, by which they were animated and kept together, and therefore which they erected in the day of their triumph. In the name of our God we must always lift up our banners, Psalm 20:5. It is fit that he who does all the work should have all the praise. - Matthew Henry