Albert Barnes Commentary Exodus 17:15

"And Moses built an altar, and called the name of it Jehovah-nissi;" — Exodus 17:15 (ASV)

Jehovah-nissi - See the margin, "Jehovah my banner." As a proper name, the Hebrew word is rightly preserved. The meaning is evidently that the name of Yahweh is the true banner under which victory is certain; so to speak, the motto or inscription on the banners of the host.

Inscriptions on the royal standard were well known. Each of the Pharaohs on his accession adopted one in addition to his official name.