Dictionary of Family Names

GALGACHUS.   In the chronicle of the kings of Scotland Galgachus is called Galdus, of which name and its etymology Gardon gives the following account:

Galgachus was Latinized by the Romans, from the Highland appellations Gald and cachach; the first, Gald, being the proper name, and the second, cachach, being an adjection to it from the battles he had fought; it signifies the same as præliosus; Gald the fighter of battles, which kind of nicknames are still in use among the Highlanders.  Colgach, Gaelic, fierce, furious, and ach, battle, skirmish.