The Ducklifors Jinx (Ducklifors) is a transfiguration jinx that transforms an organism into a duck. Fourth years and above are able to cast the spell, meaning it is likely taught in fourth year Transfiguration class.
Casting and effects
The caster will slash their wand downward to point at the target; a banana-yellow jet of light will shoot from the tip, with what appears to be a duck made entirely of brilliant yellow light soaring in front. When it hits the target, there is a burst of yellow light and when said light fades, the target is in the shape of a duck.
From the English noun "duck", with the -fors suffix attached.