Thousands of Greek words mean 'kilioi'. That is, the Greeks used 'kilioi' to mean 1000. Later the French also started using this unit. The Greek word 'kilioi' was changed to 'kilo' by the French. The French gradually became acquainted with the metric system. He started writing 'Kilo' as 1000. With the expansion of trade and commerce, 1000 became the norm all over the world. But 1000 did not last long in the same way. Instead of 1000 liters , 1000 grams , new words like kiloliter , kilogram , kiloton gradually became common . These words are too big. So write ' k' to save time . 10,000 becomes ' 10k ', 20,000 becomes ' 20k ' . And from then on, the introduction of ' k ' to mean thousand began.