It's interesting: Ok / Это интересно: Ok.

Yesterday the most popular word in the world "OK" celebrated its 175 anniversary. 

March 23, 1839 was the date when it first appeared in the  popular American newspaper The Boston Morning Post. 
We don't know exactly the origin of this word. According to one version, in the 30-ies of the XIX century there was a fashion on abbreviations, and journalists reduced phrase all correct  to "OK".