Celebrim
Legend
What?
A harbour is precisely a refuge.
Ok. Is a refuge precisely a harbor?
Yes, a harbor is a refuge but it is not 'precisely' a refuge. A harbor, in the modern sense, is a member of the super-class refuge - a particular instance of the general class. A harbor in the medevial sense was a synonym of refuge - the general class itself. We might still figuratively use harbor occasionally to mean refuge, but we'd never talk about today, finding a harbor for our horses, or finding a harbor to stay for the night, or about the army finding a habor to make camp unless we were talking about also a place to put boats. We know longer use harbor regularly to mean 'refuge'. Conversely, until the early modern, 'habor' was not primarily used to mean 'a protected refuge for boats'.
Also, it's worth noting that you don't have to 'build' a harbor. You are thinking of harbor in the sense of something constructed, but that's recent and shows that harbor is actually replacing 'quay', 'port', and 'jetty' and things like that in modern usage. Not that long ago, anyone using the term harbor would have pretty much certainly been thinking of natural features of the land, not something that was 'built'.
Language changes.