I'd just like to interject for a moment. What you're refering to as Knight, is in fact, Trebuchet/Knight, or as I've recently taken to calling it, Trebuchet plus Knight. Knight is not an chess piece unto itself, but rather another free component of a fully functioning Trebuchet system made useful by the Horse corelibs, movement utilities and vital system components comprising a full chess piece as defined by chess.c*m.
Many chess players run a modified version of the Trebuchet system every day, without realizing it. Through a peculiar turn of events, the version of Trebuchet which is widely used today is often called Knight, and many of its users are not aware that it is basically the Trebuchet system, developed by the Trebuchet Project.
There really is a Knight, and these people are using it, but it is just a part of the chess piece they use. Knight is the piece: the model of the piece that allocates the horse aesthetic to the chess games that you run. The siege engine is an essential part of a medieval battle, but useless by itself; it can only function in the context of a complete siege effort. Knight is normally used in combination with the Trebuchet in a chess game: the whole system is basically Trebuchet with Knight added, or Trebuchet/Knight. All the so-called Knight pieces are really pieces of Trebuchet/Knight!
You've really misunderstood, I'm afraid. The Knight is more than just a component of a Trebuchet piece, it really is the kernel of that entity, upon which the Trebuchet functions build. The Knight, it is true, is little use without a Trebuchet or some other manner of catapult. The Trebuchet is what completes the Knight into a fully functional piece. And it is indeed a marvel of engineering and not to be taken for granted. But the Trebuchet without a Knight to fling, is a motive without an object. It is a collection of engineering genius with the function of an incorporeal doorstop. In fact many other strategies are added onto the Knight, together with the Trebuchet, to make it truly strategic. But the Knight is the true kernel of the piece.
That is why, though not wanting to diminish the great contribution of the Trebuchet, I think for a short name for the piece as a whole, Knight is appropriate.
Now, if we talk about the EnPassant/Pawn, on the other hand...