A pind as per Hindu religious text is something that is in a circular form. And, this is how pind daan got its name in which food made in circular-ball form is offered to the soul by his/her relatives during shradh karma.
The material that is used to prepare pind during shradh is made up of kneading rice or barley flour. These pinds are made in circular form and is offered to the deceased during pind daan karma.