He was born in
Lewisham in London, the posthumous son of the Baptist missionary Bruce Etherington (1874–1907) and his missionary wife Annie Margaret. His father had died in Ceylon, leaving his mother and two older siblings to return to Britain alone. His mother remarried in 1913 to Edwin Duncombe de Rusett, a Baptist minister, but Ivor retained his original surname. In 1921 the growing family moved out of London to
Thorpe Bay on the
Essex coast, where Ivor's step-father then founded the Thorpe Hall School for Boys. In 1922 Ivor was sent back to London to be educated at
Mill Hill School. He later became a professor of mathematics at the same university. Etherington was elected a Fellow of the
Royal Society of Edinburgh in 1934. His proposers were
Sir Edmund Whittaker,
Herbert Westren Turnbull,
Edward Thomas Copson and David Gibb. He won the Society's Keith Medal for 1955–57. His doctoral students include
Henryk Minc. On his retirement in 1974, Etherington moved with his wife to
Easdale on the Scottish west coast, where the family had always had a holiday home. He died on 1 January 1994. ==Family==