Hertha Ayrton was born Phoebe Sarah Marks in Portsea, Hampshire, England, on 28 April 1854. In her youth she went by the name Sarah. She was the third child of a Polish Jewish watchmaker named Levi Marks, an immigrant from Tsarist Poland ; and Alice Theresa Moss, a seamstress, the daughter of Joseph Moss, a glass merchant of Portsea. Her father died in 1861, leaving Sarah's mother with seven children and an eighth expected. Sarah then took up some of the responsibility for caring for the younger children.