Off the top of my head

Can anyone tell me the origin of this expression? My boss at work insists that the expression was invented by him! Is he simply arrogant, strange or is he right? Can anyone find the expression used anywhere (by shakespeare or someone equally famous would suffice!) so I could confront him with a few facts?

Any help would be greatly appreciated.

Cilla Wykes

Your boss must be of a great age and have had great influence amongst the people who live in SW London - they've been using that expression (my Grandfather says) since the 1920's. On all other aspects of trhe expression I have no references to offer.