Why standing waves are called standing?

Because the peaks and valleys of wave motion do not move. Only the vibrating medium moves, at the frequency of the wave.

Standing waves are caused by a pair of matched (amplitude/frequency) travelling waves moving in opposite directions.

I will try to find a website with an illustration or video of what is meant

http://www.youtube.com/watch?v=3BN5-JSsu_4

Standing waves are called "standing" because they appear to be motionless or stationary, even though the individual components of the wave might still be moving. To understand why they are called "standing waves," we need to understand the concept of superposition.

A standing wave is formed by the superposition, or overlapping, of two waves of the same frequency and amplitude traveling in opposite directions on the same medium. When these waves meet, they interfere with each other, resulting in certain regions of constructive interference (where the amplitudes add up) and other regions of destructive interference (where the amplitudes cancel out).

In a standing wave, the points where constructive interference occurs are called "antinodes." These points have the maximum displacement from the equilibrium position. In contrast, the points where destructive interference occurs are called "nodes," and they remain at the equilibrium position.

When you observe a standing wave, it appears as if certain points along the wave are stationary while other points experience oscillation. This gives the illusion that the wave is "standing" or not moving as a whole. In reality, the individual components of the wave are still vibrating, but their vibrations are coordinated in such a way that they create a pattern of stationary regions (nodes) and regions of maximum displacement (antinodes).

Thus, the term "standing" is used to describe these waves because they appear motionless or fixed in space, despite the underlying vibrations happening within them.