1
                           general:: 
                            1. Immediately, without delay, as in He paid us back on the nail. [c. 1600] 2. Under discussion or consideration, as in The subject of the budget deficit has been on the nail for some time. [Late 1800s] The precise allusion in these expressions has been lost. Neither has any connection to hit the nail on the head (see under HIT THE BULL'S-EYE).
                        
                        
 
                        
                            American Heritage Idioms