Over time, the Norse–Gaels became ever more Gaelicised and disappeared as a distinct group. However, they left a lasting influence, especially in the Isle of Man and Outer Hebrides, where most placenames are of Norse–Gaelic origin. Several Scottish clans have Norse–Gaelic roots, such as Clan MacDonald, Clan MacDougall and Clan MacLeod. The elite mercenary warriors known as the gallowglass (') emerged from these Norse–Gaelic clans and became an important part of Irish warfare. The Viking longship also influenced the Gaelic ' or "", which were used extensively until the 17th century. Norse–Gaelic surnames survive today and include MacIvor, MacAskill, and (Mac)Cotter.