"Yoshi had a little lamb, its fleece was white as snow."
— Weapon Gallery description.
A Shepherd's Crook is Yoshimitsu's joke weapon. It is a staff with a curved end, carried by shepherds. It is a tool for catching sheep by the body or legs and controlling their movement, and is also sometimes referred to as a shepherd's staff. It is obviously not a weapon, but perhaps it is because of this that causes opponents to let down their guard.
The Weapon Gallery description is a reference to the nursery rhyme "Mary Had a Little Lamb".