The first clip type was released in 1995 along with the Sawtooth. The second clip type was released in 1997 along with the Electric Eel. It was not until 2007 and the release of the Longshot CS-6 that clips became popular and widely used.
Some of the 2011 Super Soaker blasters use a similar reloading system with an accessory called the water clip. It functions much like a regular clip, but holds water instead of darts.
Most clips can fit at least one more dart than advertised as able to do so, but this makes them more prone to jamming.
Although marketed under the name "clip", the Nerf clips are technically magazines by definition. A clip is used to feed a magazine or revolving cylinder, while a magazine or a belt is used to load rounds into the chamber.