Where does the April fool custom come from and What does April fool mean?

Since April is the first month of spring, when all things are green, it stands to reason that people are green then too, and, no more than half awake after a long winter hibernation, in prime condition to be easily hoaxed.

The custom was apparently brought across the channel from France to England about the beginning of the eighteenth century, as Jonathan Swift, in his Journal to Stella, enters under March 31, 1713, that he and others had been contriving “a lie for tomorrow.”