In Reply to: Knocking off posted by R A Collinge on November 01, 2008 at 19:37:
: Knocking off; re the first meaning- to stop work.
: It has been suggested to me that this derives from the practice of knocking a drive belt from a driving pulley to a free running pulley thus ceasing work It could apply to any belt driven machinery. In this case it was in 19th century wood turning mill. Any comment?
You are offeromg an alternate derivation to the meaning of "knock off" as "stop work," e.g., knock off for the day. The Oxford English Dictionary treats "knock" at some length, and offers examples of almost simultaneous uses (beginning in the mid-17th century) of "to knock off" as meaning, transitively, to knock someone off the job, to cause his employment to cease, whether permanently or temporarily; or intransitively, to quit work for the time being, to stop what one is doing. These uses are arranged, by the OED, as nos. 6b and 6c, respectively, following 6a, which defines "knock off," used transitively as "To strike off by or as by a blow," as in "knock one's block off." The use of "strike off" by the OED, suggests, undoubtedly accidentally, the fact that an employer used to strike off his roster such workers as he was firing or laying off.
The connection of the OED's 6b or 6c with 6a is not entirely obvious, but it is clear that the OED considers this the line of derivation for the usage you ask about. None of the examples cited makes any reference to machinery in a causative connection.
Similarly, the OED does not cite naval examples in any special sense.