"Sweat of the brow" awards copyright protection to a work
without originality, but which requires diligence and hard work. A
common example is an urtext edition of a classical composer, which
can take years of research and erudite editing, but ultimately only
produce what the composer originally intended.
"Sweat of the brow" is not upheld in the US; it is not included
in UK law, but has been upheld in court.