There are several theories of the origin of April Fool's Day specific to Great Britain, Germany, the Netherlands, and France. None of these theories offers a compelling explanation of the day's origin. However, it is a sign of the cross-cultural nature of the tradition that four different countries should attempt to take credit for it.
What is possibly the first reference to April Fool's Day can be found in the work of Chaucer.
In the Nun's Priest's Tale (written around 1392), Chaucer tells the story of the vain cock Chauntecler who falls for the tricks of a fox, and as a consequence is almost eaten. The narrator describes the tale as occurring:
This passage has caused enormous confusion among Chaucer scholars, since it appears to be self-contradictory. Could Chaucer have chosen this date purposefully, setting the tale on April 1st because of the tradition of tricks and foolery associated with the day?
Most editors of Chaucer don't think so. The most popular interpretation of this passage is that Chaucer meant May 3, so editors often change the text to read "Syn March [was gon]". However, the historian Peter Travis has argued that Chaucer did not intend to provide a precise date at all, but was instead purposefully using confusing language in order to parody the language of Medieval philosophy.
Whatever Chaucer may have meant, we can't conclude, based on these few lines, that he was aware of a custom of playing pranks on April 1st.
Almost every culture in the world has some kind of festival in the first months of the year to celebrate the end of winter and the return of spring. Anthropologists call these "renewal festivals." Often they involve ritualized forms of mayhem and misrule. The wearing of disguises is common. People play pranks on friends and strangers. The social order is temporarily inverted. Servants might get to order around masters, or children challenge the authority of parents and teachers. However, the disorder is always bounded within a strict timeframe, and tensions are defused with laughter and comedy. The social order is symbolically challenged, but then restored, reaffirming the stability of the society, just as the cold months of winter temporarily challenge biological life, and yet the cycle of life continues, returning with the spring.
April Fool's Day has all the characteristics of a renewal festival. For one day forms of behavior that are normally not allowed (lying, deception, playing pranks) become acceptable, and yet the disorder is bounded within a strict timeframe. Traditionally, no pranks are supposed to be played after 12 o'clock noon of the first. Social hierarchies and tensions are exposed, but hostility is defused with laughter.
The French also have a theory that traces the origin of the custom back to the abundance of fish to be found in French streams and rivers during early April when the young fish had just hatched. These young fish were easy to fool with a hook and lure. Therefore, the French called them 'Poisson d'Avril' or 'April Fish.' Soon it became customary (according to this theory) to fool people on April 1, as a way of celebrating the abundance of foolish fish. The French still use the term 'Poisson d'Avril' to describe April Fool's Day pranks. They also observe the custom of giving each other chocolate fish on April 1.
British folklore links April Fool's Day to the town of Gotham, the legendary town of fools located in Nottinghamshire. According to the legend, it was traditional in the 13th century for any road that the King placed his foot upon to become public property. So when the citizens of Gotham heard that King John planned to travel through their town, they refused him entry, not wishing to lose their main road. When the King heard this, he sent soldiers to the town. But when the soldiers arrived in Gotham, they found the town full of lunatics engaged in foolish activities such as drowning fish or attempting to cage birds in roofless fences. Their foolery was all an act, but the King fell for the ruse and declared the town too foolish to warrant punishment. Ever since then, according to legend, April Fool's Day has commemmorated their trickery.
On April 1, 1530 a meeting of lawmakers in Germany was supposed to occur in Augsburg in order to consider various financial matters. Because of time considerations, the meeting did not take place. But numerous speculators, who had bet on the meeting occurring, lost their money and were ridiculed. This is said to have been the origin of the tradition of playing pranks on April 1.
On April 1, 1572 Dutch rebels captured the town of Den Briel from Spanish troops led by Lord Alva. This military success eventually led to the independence of the Netherlands from Spain. A Dutch rhyme goes: "Op 1 april / Verloor Alva zijn Bril." This translates to: "On April 1st / Alva lost his 'glasses'". "Bril" means glasses in Dutch, but is also a pun on the name of the town, Den Briel. It is claimed that the tradition of pranks on April 1st arose to commemorate the victory in Den Briel and humiliation of the Spanish commander.
Take your pick of the theories but get into the tradition and hopefully play some practical jokes today in the spirit of fun!