Origin of "Around the clock" or "Round the clock"? [closed]

Solution 1:

What do you mean it's unidentifiable?

The origin seems pretty obvious to me. The hands of a clock go round. The tips of the hands make circles as they turn. If you say your team is working around the clock, it means that you keep working while the hour hand goes around several times.

Solution 2:

The origin appears to be literal, its usage is from WWII according to Etymonline:

Round-the-clock (adj.) is from 1943, originally in reference to air raids.

Google Books suggest the expression became popular from the 1940s but there are earlier sporadic usages which date back to early 20th century.