每日口說挑戰 “OK”的由來到底是什麼？ (What is the origin of the word 'OK'?)

今日挑戰句子

Unfortunately, historical evidence enabling the origin of this expression to be finally and firmly established, is hard to unearth.

可惜的是，可以一勞永逸地確定這個表示法的來源證據很難被發掘。