From a Norman French name, Raulf, a contracted form of the Germanic personal name Radulf, derived from rād ‘counsel’ + wulf ‘wolf’. The spelling with -ph is due to classical influence in the 18th century.
Scottish and northern Irish: habitational name from what is now a deserted village in the parish of Barkby, Leicestershire. This is named from Old English hamel ‘crooked’ + dūn ‘hill’. Hamilton near Glasgow was founded by the Hamiltons and named after them. In Ireland, this name may have replaced Hamill in a few cases. It has also been used as the equivalent of the Irish (Cork) name Ó hUrmholtaigh.