|Easton's Bible Dictionary|
Jehovah my banner, the title given by Moses to the altar which he erected on the hill on the top of which he stood with uplifted hands while Israel prevailed over their enemies the Amalekites (Exodus 17:15).
Int. Standard Bible Encyclopedia
je-ho'-va nis'-i (yahweh nicci, "Yahweh is my banner"): So Moses named the altar which he reared to signalize the defeat of the Amalekites by Israel under Joshua, at Rephidim (Exodus 17:15). Septuagint translates "the Lord my refuge," deriving nicci from nuc, "to flee." Targum Onkelos reads, "Moses built an altar and worshipped on it before Yahweh, who had wrought for him miracles" (niccin). The suggestion is that the people should rally round God as an army gathers round its standard. He it is who leads them to victory.
Jehovah-nissi (1 Occurrence)
Exodus 17:15 And Moses built an altar, and called the name of it Jehovah-nissi; (ASV DBY WBS YLT)