to let down: to lower something on a slackening rope or by hand, so it descends at the pace of whoever is holding it
Behind this verb is the picture of a rope going slack. It does not simply say that something moved downward. It says that someone above is paying out a line, or easing a grip, so that whatever is attached comes down at the speed they choose. The load stays under the control of the people holding it, which is why the word turns up wherever people lower something carefully rather than drop it.
The New Testament uses it for rescue, for fishing, and for seamanship:
- friends lowering a paralyzed man on his mat through a hole they had dug in a roof
- disciples lowering Paul over the wall of Damascus in a basket at night
- fishermen letting their nets out into deep water at a word from Jesus
- sailors lowering the ship's gear, and later its small boat, in a storm off Malta
Two nearby verbs are worth keeping apart from it. καθίημι also means to let something down, and Acts 9:25 uses both words in a single clause about Paul's escape, but it watches the object travel downward rather than the rope being paid out. καθαιρέω means to take something down and remove it, as when Jesus' body was taken down from the cross, so the thing comes away rather than being eased down on a line.
Nothing about the word is figurative in the New Testament: every use is a physical lowering. What varies is who is doing it and why. In each scene the descent is deliberate, whether it is a rescue that gets a man to Jesus, an order a tired fisherman obeys against his own judgment, or a crew trying to survive a storm.