A name given for strength in battle. Historians relate the following tradition: This family was anciently settled on the Scottish border; their original name was Fairbairn, which was changed to Armstrong on the following occasion: An ancient king of Scotland having had his horse killed under him in battle, was immediately re-mounted by Fairbairn, his armor-bearer, on his own horse. For this timely assistance he amply rewarded him with lands on the borders, and to perpetuate the memory of so important a service, as well as the manner in which it was performed (for Fairbairn took the king by the thigh, and set him on the saddle), his royal master gave him the appellation of Armstrong. The chief seat of Johnnie Armstrong was Gilnockie, in Eskdale, a place of exquisite beauty. Johnnie was executed by order of James V., in 1529, as a "Border Freebooter." Andrew Armstrong sold his patrimony to one of his kinsmen, and emigrated to the north of Ireland in the commencement of the seventeenth century. The Armstrongs were always noted for their courage and daring. In the "Lay of the Last Minstrel," when the chief was about to assemble his clans, he says to his heralds: "Ye need not go to Liddisdale, For when they see the blazing bale Elliots and Armstrongs never fail."

Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.

ARMSTRONG. Doubtless from strength of limb, as displayed in war and athletic sports. Armstrang is the same, and Strongi'th'arm, a cognate surname. The well-known border clan of Armstrong were of old a truly armipotent race, and Johnnie A., their chief, the great fi'eebooter, lived in Eskdale ; while Liddesdale was another hahitat of the family.

Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.