[bryanrasmussen]

If it were birthed it might be smarter to say orphaned or alienated or something that follows the parentage metaphor instead of unmoored.

If it were berthed it would make more sense to be something like "The destiny of all books is to become unmoored from the time where they were originally berthed".

But it is more common in English to use birthed as created than this kind of extended nautical metaphor.

And it is more common for people to mix their metaphors, especially when they are trying to sound clever.

Therefore I think they mixed their metaphors a bit.

[basil-rash]

> But it is more common in English to use birthed as created than this kind of extended nautical metaphor.

The question isn't whether birthed is more common than extended nautical metaphors in general, the question is given that a nautical metaphor is already in place, what is the likelihood that metaphor is being extended, versus trampled and replaced with another?

> If it were berthed it would make more sense to be something like "The destiny of all books is to become unmoored from the time where they were originally berthed".

Only if the author is assuming the ship has been berthed many times. It might just as easily have been berthed once and adrift ever since. Being berthed in no way implies repetition.

[bryanrasmussen]

I guess your assumption about repetition is due to originally, because otherwise I don't see anything that could lead to that assumption, but that assumption is also rather tenuous, because originally berthed would still be a relevant phrasing to use if the boat becomes unmoored.

That is to say originally berthed also works for having been berthed once and adrift ever since, at least in English which tends to be forgiving about this kind of thing.