Why do Czech Airlines have the airline code (IATA airline designator) "OK"? Is there any specific reason why Czech Airlines have OK as the IATA airline designator?

According to an urban legend: 


  Urban legend says that when airline names were awarded -- I believe in 1946/46 -- the Czechoslovak delegation, not versed too much in English, just said OK to the questions asked. So the name stuck.


I do not much believe in the legend, but still the question remains.

I would expect that at the time when the (then) Czechoslovak Airlines were assigned the code, there were not so many airline operators as nowadays and that CS (or something similar) must have been available.
It starts with the International Telecommunications Union, which assigned radio call sign prefixes for each country in 1927. The OK prefix was assigned to Czechoslovakia. Other than the largest countries (US, USSR, UK, France, etc.) there seems to be no specific pattern to the assignments. When ICAO assigned aircraft registration prefixes for each country it usually based them on the ITU prefixes. In 1947, when ICAO assigned 2-digit airline identifiers they chose to use the country’s registration prefix for Czechoslovakia’s flag carrier. IATA originally based their airline ID’s on ICAO’s 2-letter ID’s. In 1982 ICAO changed to their current 3-letter format.