KY is the first letter of "empty" extracted from Japanese (literally translated as "I can't understand atmospheric air"). It means that you didn't look at it and didn't react properly according to the atmosphere and the other person's face.
For example, Naruto's blast ED7 "Long Kiss Goodbye" says: at any time, りすぎ 12398ky. Sometimes I always say too many inappropriate words.
Extended data:
Ky's general idea is that he doesn't understand the atmosphere and often makes inappropriate behaviors and says inappropriate things. Or talk about people who don't appear, such as BC, when there is only a, and this person is considered to be in KY.
This word was first used by middle school students. Later, former Japanese Prime Minister Shinzo Abe failed in the Senate election but insisted on not resigning. Politicians and the media accused "the Prime Minister is really KY", so he quickly became popular. Later, KY-style Japanese appeared. Specifically, the first letter of romaji was taken from the corresponding Japanese phrase, such as am = でまたね(atode· Matanet).
Related dictionaries have also appeared in Japan (for example, KY Japanese compiled by Yasuo Kitahara collects popular Roman abbreviations), which is enough to show how popular KY Japanese is.
References:
Ky Baidu encyclopedia