OK 也可以写成 Okay，但 OK 不是 Okay 缩略来的。根据《新牛津英汉双解大词典》在 OK给出的“语源”，OK 很可能是 orl korrect （= all correct）的缩略形式。

《新牛津英汉双解大词典》的相关原文如下：
mid 19th cent. (originally US): probably an abbreviation of orl korrect, humorous form of all correct, popularized as a slogan during President Van Buren's re-election campaign of 1840 in theUS; his nickname Old Kinderhook (derived from his birthplace) provided the initials.