A Falx is a Latin word originally meaning Sickle, but was later used to mean any of a number of tools that had a curved blade that was sharp on the inside edge such as a Scythe. Falx was also used to mean a weapon, particularly that of the Thracians and Dacians, and later a siege hook used by the Romans themselves. Due to the scythe-like nature of the falx it is feasible to see why this weapon type is exclusively for Dark Knights.