Knock Off
Meaning
To finish work for the day. Alternatively, to work quickly and complete a task – similar to polish off. A third alternative is a slang term meaning to steal.
Origin
The origin of the first meaning could possibly be from the habit of knocking a special beat to indicate a change of oarsmen in slave galleys. That’s speculation but several of the earliest references to the term come from a nautical source. For example, William Clark Russell’s novel An ocean tragedy, 1890:
“We were forced to knock off through sheer fatigue.”
The second meaning to work quickly and complete a task is known by the early 19th century.
