Roger Coffin had been sailing with Captain Teach on the Queen Anne's Revenge for a year when the mutiny against Teach sprung up.
Teach had liberated him from La Concorde de Sainte-Malo, a slave ship bound for Barbados. His slave name had been Rogue Re Grainge, on account of the African's unexplainable bushy red hair. The English began calling him "Roger" and gave him the last name "Coffin" due to the way they found him in the hold of the Concorde. His new found freedom and fortune caused him to flash a toothy smile for all to see. After a time he was alternately called "Grinning Roger" or "Jolly Roger Coffin", sometimes simply "Grins".
He proved himself a capable seaman; quick with the cutlass, harpoon and dagger when pressed into a fight, but the seajacks loved him for his singing voice and his smile that could light up the quarterdeck or put the fear of God in his enemies' hearts in the midst of battle.
When that mutiny started over the division of spoils, he speared the ringleader in the heart with his harpoon and casually toasted his captain, Edward "Blackbeard" Teach, known as the "Devil" to most men in 1716, with his day's ration of grog.
Teach was so impressed he used that image of "Grins" on the flag of Queen Anne's Revenge to inspire fear in his enemies with his "Jolly Roger".