The Ferz
The Ferz is a piece from the original game of Chess, where it occupied the position on the board that the modern Queen does now.The Ferz moves one square diagonally, so from e4, a Ferz can reach d5, f5, f3, or d3. The Ferz, like the Bishop, can never get to 32 of the 64 squares on the board...
By itself, the Ferz is too weak a piece to be of much interest, but its power can be combined with the powers of other pieces to make new and interesting ones. By itself, it is worth less than a Pawn and a half, but in combination with other pieces it is worth half a Knight, more or less.
The funny notation for this is simply the letter F, because the Ferz is one of the basic geometric ingredients used in the recipes for other pieces.
The funny notation could also be F1, meaning that it is a one-step diagonal mover. Please notice that F7 (on an 8x8 board) is the Bishop; the Bishop is nothing but an extension of the basic geometrical move of the F.
The Pawnless endgame with King and three Ferz (not all on the same color square) is winnable. Two Ferz (and the King) can confine the enemy K to a corner and stalemate, but it isn't easy.