To bone up

 
The phrase to bone up means to revise; study a subject in depth; to study intensely, usually at the last minute as for an exam.
As with many phrases the origins are uncertain. One suggestion is that it relates to a Victorian publisher and bookseller Henry Bohn (1796-1884) who produced many study primers in Latin and Greek. If he had been the cause of th pjrase one might have expected it to appear as Bohn up on occasion but it never does. An alternative, and more tenable theory, is that it derives from the practice of using bones to polish leather. So, boning up was polishing or refining one's knowledge.

It's a shame that the Henry Bohn theory doesn't stack up because Liverpool still boasts a Henry Bohn bookshop. I don't know if the proprietor was ever a Henry Bohn or whether the name simply derived from the bookselling world's more famous predecessor.