rhabdos

At bottom this is a stick: a piece of wood a person can close a hand around. Everything in this meaning follows from that plain object, and what changes from verse to verse is only what somebody is doing with it.

The New Testament puts it to work in a few ordinary ways:

• the staff a traveler takes on the road, or an old man leans on
• the stick raised to strike someone in correction
• a stout stick used as the measure of how thick and rigid something else is
• the one particular staff of Aaron, kept as a token after it sprouted

Because a single Greek word covers all of that, English Bibles switch between "staff", "rod", and "stick" to suit the job in view, and the switching can hide the fact that one word is behind them all. The word itself says nothing about size, decoration, or purpose; the sentence around it supplies that. In Revelation 11:1 the measuring instrument John is handed is actually a reed (κάλαμος), and this word only describes how stiff and staff-like that reed was.

Behind the Greek stands a family of Hebrew words for the same object, chiefly the shepherd's and traveler's staff (מַטֶּה) and the rod that both beats and rules (שֵׁבֶט), which the Greek Old Testament regularly renders with this one word. That inheritance is why a New Testament writer can reach for it whether he pictures a shepherd's crook, a traveler's stick, or the staff Moses stretched out over the sea.

A ruler's staff is still a staff, and that is where this meaning gets its force. The scepter of an ancient king was not a jeweled trinket but a solid rod, the same sort of thing a shepherd carried, held up to say that this hand governs. So when Hebrews quotes a psalm about a throne and calls the king's staff a scepter of uprightness, the picture is of a rod that rules straight instead of crookedly.

Revelation takes the same image somewhere harder. Three times a ruler shepherds the nations with an iron rod, a phrase lifted from Psalm 2. In the Hebrew of that psalm the ruler breaks the nations like pottery; the Greek Old Testament read the same consonants as "shepherd" instead, and Revelation follows the Greek while keeping the shattered pottery beside it. The result is deliberately double: the one who governs the nations does it with a shepherd's implement made of iron.

The Hebrew words behind this use, the rod that both beats and rules (שֵׁבֶט) and the staff a king holds out in court (שַׁרְבִֿיט), keep the same everyday feel. English "scepter" has drifted toward the ceremonial; the Greek word never loses its grip on the wooden stick, and the authority lies in whose hand holds it.