On April 1st, above all children make pranks and stick at the back of someone a fish made in paper. When the fish is discovered, the child who sticked the fish say "poisson d'avril!" and it is the same for pranks.
We don't know exactly the real story. A lot of versions were told. The most known remains that Charles IX, in 1564, instaured the first day of year was on January 1st instead of on April 1st. On April 1st everybody used to offer gift each other. The pope Gregoire XIII spread the gregorian calendar to Christian nations in 1582. From January 1st 1565, was the new year day.
Why this day became a foolish day?
Some people met difficulties to remember the new year day and some ignored the reform (No TV, no Internet at that time! 😉). They carried on celebrating the new year day on April 1st. To mock at them, some guys made jokes or hung a fish at the back of their victim. When the fish was found out the jokers shouted "Poisson d'avril"! They also made fake presents.
Why a fish?
Once again, I read different stories. One told that fishing were not allowed due to the reproduction of fish and it was a period which was benefit for fishers.
The other told that fish is a symbol of the end of fasting (careme). It was forbidden at this period to eat meat for christians. Prankers offered fake fish. the fish was the graphic symbol of Christianism, a sign of recognition. It is made wich two arks. Fish "poisson" would come from the corruption of passion "passion". A corruption is a phonetic transformation of a word.
A few expressions about fish
Etre comme un poisson dans l'eau (to be like a fish in water): To feel well or to be at your ease in the place where you are or what you do.
Finir en queue de poisson (ending in fishtail): an event or a story which ends roughly and disappointingly.
Faire une queue de poisson (making a fish tail): turning down for a vehicle abruptly in front of the car which it just overtaken.
Noyer le poisson (drowing the fish): muddling up somebody
Engueuler quelqu'un comme du poisson pourri (calling somebody every name under the sun): to insult somebody or shouting after someone.
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