According to this theory, April’s Fool goes back to 1564 when King Charles XIV changed the calendar around, moving the start of the year from late March to early January. Not everyone was quick to catch onto the change and some people kept celebrating New Year during the week that fell between March 25th and April 1st. And these people had jokes played on them. Pranksters would surreptitiously stick paper fish to their backs and so victims of the pranks were called Poisson d’Avril, or April Fish—which, to this day, remains the French term for April Fools. Why fish… well, that we don’t know but it stuck for some reason.
[This post was initially published on this blog on April 1st, 2010. No joke!]