The Hebrew word ner means lamp or light. It refers to an oil lamp — a small clay or metal vessel filled with olive oil and fitted with a wick that provided illumination in ancient homes and in the tabernacle/temple. The word is used both literally for a physical lamp and figuratively for life, prosperity, divine guidance, and the continuation of a royal dynasty.
The lamp is one of the richest metaphors in the Old Testament. God's word is described as a lamp to the feet (Psalm 119:105), providing guidance through life's darkness. The lamp of the wicked being extinguished represents the end of prosperity and life (Proverbs 13:9). Most significantly, God promises David that his descendants will always have a lamp in Jerusalem (1 Kings 11:36) — a messianic promise pointing to Christ, the Light of the World. The perpetual lamp in the tabernacle symbolized God's unending presence among His people.