"Then she saw a boy standing at a corner, with a small hurdy-gurdy on his back and a tortoise in his arms."
Painting of an organ grinder
Public DomainPainting of an organ grinder - Credit: Antoni Kozakiewicz
Organ grinder and monkey (1892)
Public DomainOrgan grinder and monkey (1892) - Credit: Overpeck

A hurdy-gurdy is a type of street organ or  barrel organ. This is a mechanical musical instrument which is played by turning a handle. Inside the barrel organ is a cylinder studded with pins and staples. As this cylinder is turned, different tunes are played automatically.

Those who played barrel organs in public to earn money used to be known as organ grinders. Sometimes their barrel organs were free standing; sometimes they had to be carried. Some organ grinders had performing monkeys as an extra attraction.

Perhaps the 'extra attraction' of the little boy in Frankfurt was the tortoise.