The foil was invented in the middle of the 18th century as a
training weapon in order to practice fast and elegant thrust
fencing. Fencers blunted the point by wrapping a foil around the
blade or fastening a knob on the point. Another factor in the target
area is that foil rules are derived from a period when dueling to
the death was the norm. Hence, the target area is the torso,
where the vital organs are.
The épée evolved from civilian weapons such as the 17th century
small sword. The épée developed when authorities in the 19th
century decided that they did not like the killing aspect of the duel
and changed it to a "first blood" event. This required much more
skill, as a nick on the wrist or other exposed area could end the
duel. Today’s épée fencing very much resembles the 19th century
dueling’s “first blood”.
The saber was originally a heavy curved sword used by cavalry
soldiers. Over the centuries, the blade has become much lighter
and thinner and perfectly straight. The guard completely covers
the hand. The target area for saber bouts is anywhere above the
waist (which is reminiscent of horseback days).