Hm. To me it always connoted secret knowledge of undocumented features of a system. Now it seems to cover any clever idea, and some less-than-clever.
Books have very few undocumented features, but the RFID hidden in the spine might be one. Now, if you could reprogram that so the system thought the book you just stole had a negative price tag, and the police came and gave you a reward... that's what I call hacking!