In Reply to: Knock off posted by Alan Brown on September 01, 2010 at 13:49:
: 'Knock off'. It is possible that the phrase dates back to the period of massed archers,when the standard instruction to ease the bow by releasing the string was to 'knock off' (the string) with the thumb. Easing the bow meant that the work, fighting or practice for the day was done.
No, it isn't possible. The phrase "knock off" meaning "to stop working, or to cause someone to stop working", dates back only as far as the mid-17th century, more than a hundred years after the use of archers in warfare had been abandoned and regular archery practice had thus ceased to be a part of English life. If "knock off" had ever been used to mean "ease the bowstring with the thumb", as you claim (and the Oxford English Dictionary knows no such usage), it would no longer have been in common parlance by that time. (VSD)