This might be a late reply, but I have been following up my Orkney Island family: the Ironside part may have come from Monquhitter. John Findlater came from New Deer in Aberdeenshire and my grandfather, Alexander Mathers Ironside was born illegitimate on Dec 9, 1861, in Orkney, to his daughter Jessie (or Janet/Jannet) Findlater, . The father was Robert Ironside, from the birth Certificate of his younger brother John who was registered as an Ironside. The 1861 census has Robert Ironside as being born in Monquhitter, Aberdeenshire. By the 1871 Census Alexander Mathers Findlater had also changed his name and become an Ironside.
Janet Findlater (born in New Deer, Aberdeenshire) married George Paterson on July 14, 1870 when he was 69 and she was 28. Thomas Gunn Paterson was born 1872 (died 1955). George Paterson died in 1879 and his death certificate is signed by my grandfather as "Alexander M Ironside (Stepson)".
I do not know if there is any connection but thought I would pass this on!