> PIE. leubh-o-z
> (But there is another homonymous <leubh-> "love".)
Perhaps it's not an aspirated "b"?
If it's possible, perhaps "liber" etc. arise from some alteration of
the word "*litho," meaning "rock." But it seems to be of non-PIE
origin, my dictionary suggests. (Heritage Illustrated dictionary of
the English Languae International Edition)
The closest I can find is *skri:bh, an extension of several degrees on
*sek, "to cut". Also, there's the idea of a book a a teacher - that
would go back to *deik, "to show" or "to direct." So, what kind of
ending would make "*deik" a noun meaning "shower" or "director"