IRONSIDES, a nickname given to one of great bravery, strength or endurance, particularly as exhibited in a soldier. In English history Ironside or Ironsides first appears as the name of Edmund II., king of the English. In the Great Rebellion it was first given by Prince Rupert to Cromwell, after the battle of Marston Moor in 1644 (see S. R. Gardiner's History of the Great CM War, 1893, vol. ii. p. i, and Mercurius civicus, September 19-26, 1644, quoted there). From Cromwell it was transferred to the troopers of his cavalry, those "God-fearing men," raised and trained by him in an iron discipline, who were the main instrument of the parliamentary victories in the field. This (see S. R. Gardiner, op. cit. iv. 179) was first given at the raising of the siege of Pontefract 1648, but did not become general till later.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)