The behavior of the Foucault pendulum can be understood by using some basic geometrical reasoning. First, we will consider the case of a pendulum suspended above the center of a rotating platform (like a merry-go-round). A person standing on the rotating platform holds the pendulum bob and then lets it go. The pendulum will swing back and forth along a fixed plane while the platform spins counterclockwise beneath it. However, an observer standing on the platform will see the pendulum's plane of oscillation rotate, or precess, clockwise. The simulation below shows this scenario from two points of view: that of an observer on the ground, and that of an observer standing on the rotating platform.
Note that the pendulum's motion is not confined to the highlighted plane because the pendulum is released by the observer on the platform. That means the pendulum, along with the platform and the stick figure person, is already moving relative to the ground (in a counterclockwise direction) when it is released. As a result, the pendulum does not move back and forth within the highlighted plane but instead moves in a narrow ellipse that is aligned with the plane.
The situation depicted above is exactly analogous to the case of a Foucault pendulum at the North Pole of Earth. In that case the pivot point is stationary, because any point on the Earth's axis of rotation will remain stationary as the Earth spins. The pendulum will swing back and forth in a fixed plane while the Earth rotates counterclockwise beneath it. Observers standing on the Earth will see the pendulum precess clockwise, completing a full precession once every (sidereal) day.
In just the same way, a pendulum at the South Pole will appear to precess counterclockwise (since at that location the ground is spinning clockwise) with a full precession each sidereal day.