There was also another explanation.
Watanuki --> Were-tanuki (Raccoon)
It's the day when raccoons take the form of humans.
In Japan, raccoons are known as avid liars.April 1st can also be read as "Watanuki."
There was a story in the ancient times that, during this day, people reinvented garments by removing the cotton from padded clothes.
"Wata" = cotton; "Nuki" = remove