Black in his Surnames gives the origin as the place-name Grundwatter in Orphir, Alexander in Gyre,Orphir died in 1686, Edward in Tankerness was captured by the pressgang in 1812.
An Orkney Groundwater was concerned in the horrible murder of Janet Cornfoot a supposed witch in Pittenweem, Fife, 1705.
Bests,
Skoosh.