I asked a group of young women if they could throw some common—and not so common—Japanese abbreviations at me.

Old standards, of course, are OL (Office Lady), OB (Old Boy, as in an alumni network), and TPO (Time Place Occasion).† Ones I hear rather frequently now include CA (Cabinet Attendant, i.e. stewardess, who for the longest time were called “sutchi”) and KY (Kuki-o Yomenai, which refers to someone who can't read the mood of a situation; i.e. someone who just doesn't get it.)

Newer abbreviations, though, can be rather funny.

“PK,” one of the girls in the back of the classroom called out to peals of laughter.

"PK?" I asked. "PK, as in penalty kick?"

The girl giggled and said, "Yes, sensei, penalty kick."

I could tell that she wasn't telling me the truth. "C'mon, what does it really mean?"

"It's embarrassing."

"Yes, but, you brought it up."

"パンツ食い込み (pantsu kuikomi)."

"Aa-ah," I said, as the image hit me. (Don't recommend googling that when you're at work, by the way.)

And then the girls rolled about in the aisles between their desks, as they do.

PK is no laughing matter. According to a highly scientific study conducted by Wacoal, a manufacturer of lingerie, some 80 percent of Japanese junior and senior high school girls, namely JC and JK, are troubled by PK. Fortunately, the good people at Wacoal have come to the aid of these fair damsels in distress with a new line of inexpensive skivvies called NPK, or “Non-P. K.” that retail for ¥1,100. SM no more! Shimpai muyō (心配無用).

More abbreviations include:

HK 話、変わるけど（Hanasi Kawarukedo）

HM 話し戻る けど（Hanasi Modorukedo）」

MK5 マジ（Maji））で切れる（Kireru）5秒前

WK しらける from 白＋蹴る＝White＋Kick

AY 頭（Atama）」+「弱い（Yowai）

AKY あえて空気読まない which is further abbreviated to KY

MMK モテて、モテて、困る (異性から人気があり過ぎたり、多数の異性から言い寄られて困るという場合に使用する)

For more of these abbreviations, go here.

Most Japanese believe that TPO is English, but it was actually thought up by Ishizu Kensuke (石津 謙介), the founder of Van Jacket, an apparel maker popular between the 60s and 80s.