There is a peculiar name for God in the Bible יהוה נִסִּי (Adonai Nissi). Moses called God by this name when He gave Israel a victory over Amalekites in the wilderness in Ex 17:15. Most English Bible translations render it as “LORD is my Banner”, communicating the idea of a flag.
In ancient Hebrew, however, נֵס (nes) can mean a flag, a sign or an ensign (Jer. 51:12; Is. 49:22). However, it is more nuanced than that. The word נִסִּי (nissi) “my banner” is connected by its root to verb לָשֵׂאת (laset) which means to carry, to lift, to raise up.
This verb נָשָׂא (nasa) appears in many biblical verses in various forms and has always something to do with upward motion and carrying which makes perfect sense in context of a banner or a sign. In Num 26:10 the death of the songs of Korah וַיִּהְיוּ לְנֵס (vayihyu lanes) “became as a warning sign” to those who watched.
In Num 21:8 Moses set a bronze serpent on a נֵס (nes) a pole. In that sense the word נֵס (nes) was understood not simply as a flag or banner, but idiomatically as a miracle, a supernatural sign. This is exactly how it is used in Modern Hebrew today.