What is the etymology of パイセン?


As a slang term for [先輩]{せんぱい}, パイセン doesn't seem to be very popular. I
occasionally hear it used among young people. Is it mostly a term used in
Tokyo (dialectal)? Where did it come from? My impression is that this term has
been around so long that it is unlikely Internet slang.




As Japanese can be written vertical too, Paisen results in reading the kanji
from below to above. It is an internet slang popularized by comedy artists
[Yano and Yano](https://matome.naver.jp/odai/2142185449328216601).

