George a' Green
As good as George a' Green. Resolute-minded; one who will do his duty come what may. George a' Green was the famous pinder or pound-keeper of Wakefield, who resisted Robin Hood, Will Scarlett, and Little John single-handed when they attempted to commit a trespass in Wakefield.
Were ye bold as George-a-Green, I shall make bold to turn again.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894