katagō

This is the ordinary Greek verb for leading or bringing (ἄγω) with "down" built onto the front of it. A person or a thing is moved from a higher place to a lower one: from the hills of Jerusalem down to the coast, from the soldiers' barracks down to the council chamber, from heaven down to earth. The one doing the moving is always acting on someone or something else, which is what separates this verb from the common word for going down under your own power (καταβαίνω).

Most of its New Testament appearances belong to Luke, and most of those to the story of Paul's arrest. Plotters and officials keep asking that Paul be brought down from the fortress to the Jewish council, and the Roman commander finally does it. The descent is literal, since the barracks stood above the temple courts, but the word is also doing the work of a courtroom expression in English: to produce a prisoner before the court.

The use that catches readers off guard is at sea. Greek sailors spoke of heading up onto the open water and coming back down to land, so this verb became the standard way to say that a ship put in at a harbor. When Acts reports that the travellers landed at Sidon, this is the word, paired all through the voyage with its opposite (ἀνάγω), the verb for setting sail.

Paul then reaches for the same plain verb for the largest descent imaginable. Answering the question "Who will go up into heaven?", he explains that this would mean bringing Christ down. Nothing technical is going on: it is the everyday word for fetching someone from a higher place, which is exactly what gives the argument its force. Nobody has to go and get Christ, because the message of faith is already close at hand.