to be low or become low, and so to bring something low: to lay it flat, cast it down, or humble it
At its core this word is about height, and about losing it. Something that stands high, a mountain, a wall, a tower, a person's rank, comes down. The word covers both sides of that motion: to sink low yourself, and to be the one who pulls something else down.
The Bible uses it two ways. Sometimes the lowness is literal: hills are leveled, a proud city's walls are dragged to the dust, a voice speaks up from the ground. More often it is a picture of status and pride. The arrogant are cut down to size, the exalted lose their crown, and God is the one who does the leveling. This is why the word so often stands right next to its opposite, to be high or to lift up: God lays one person low and raises another, brings down the proud and holds up the humble.
The two uses are not really two different words. They are the same idea, physical lowness, used plainly in one place and as a picture in another. So the same verb that flattens a mountain also flattens human pride, and the reader is meant to hear both at once.