Outside of being Willington's apocope, so can William's. In addition you can also use Willy. Willi is also the surname of a Swiss pediatrician (named Heinrich Willi) who together with also Swiss doctors Andrea Prader and Alexis Labhart did countless studies on rickitism, hypotonia. He made a lot of contributions sobe the management of Neonates. He participated in studies on Prader-Labhart Syndrome - Willi, which is characterized by the hypotonia of babies and the inability or difficulty in sucking.