refuge: a place you run to for cover and safety, whether a rock in a storm or God himself
Machseh names the place where someone in danger takes cover. It is built from a verb that means "to flee for shelter," so the word carries the memory of running: it is the spot where the running stops. At its most physical it is a rock you crouch behind in a downpour or the crag a small animal disappears into.
From that concrete picture the word grows into Israel's favorite way of confessing trust in God. Of its twenty appearances, most are in the Psalms, and there it almost always says the same thing: God is my refuge. The striking feature is that the word never quite loses its physical edge. When a psalmist calls God his refuge, he is not naming a vague inner feeling but something more like a real, located place he has run to and now stands inside.
The prophets can turn the word against people who trust the wrong thing. Isaiah mocks Jerusalem's rulers for making a lie their refuge: they have used the language of faith for a shelter that will not hold. It is the same word, in the same shape, deliberately turned inside out.
These are not separate words but one word at different distances from its origin: the rock, the God who is like a rock, and the false shelter that pretends to be one.