While searching kirk session minutes for a one place study, I've come across a Mary Ann Unthank who was 'lately come' to the parish of Walls, Orkney, according to a minute of 1 July 1841 . She was the wife of William Wilson and had been a member of a Methodist church in Hull for two years. William was from Orkney, almost certainly from Walls, and could well have been a seaman. Their marriage appears to have been registered in the Sculcoates registration district, East Yorkshire, in the 2nd quarter of 1841 and they were recorded in Walls at the time of the 1841 census, both aged 20.
William and Mary Ann are no relation to me but the very unusual surname has intrigued me and I hope that someone may "recognise" Mary. There is a baptism record for a Mary Ann Unthank, 27 Dec 1818, Sculcoates, daughter of Robert and Susannah, which may be her.