It is. Well, the word at least, it doesn’t appear in Websters. But that’s okay.
For the longest time, swivel casters were made of three basic pieces, a yoke, a plate, and a kingpin. Between the yoke and the plate is the bearing race, the kingpin holds it all together. It works well enough for most applications. They can be heavy duty, but then it starts getting expensive, using tapered bearings or hot forged steel. The kingpin has always proved to be the single greatest point of failure in a caster.