The motto appears in French and translates into English as "God and my right". (A fuller version of the motto is also quoted as "God and my right shall me defend". Originally spelled Dieut et mon droict in early Modern French, the t in Dieut and c in droict were later dropped in accordance with present French orthography.
For the Royal coat of arms of the Kingdom of England to have a French rather than English motto should not be considered unusual, given that English had only recently replaced French as the language of the English Royal Court and ruling class. Also appearing on the Royal arms is the Old French motto of the Order of the Garter, which appears on a representation of a garter as Honi soit qui mal y pense, ("shame upon him who thinks evil of it").
Dieu et mon droit was allegedly first used as a password by King Richard I in 1198 at the Battle of Gisors, when he defeated the forces of Philip II of France. This implies that Richard owed his royalty to no power other than God and his own heredity, and was therefore subject to no earthly power nor other monarch. This can be taken as a direct reference to the doctrine of the Divine Right of Kings.
Dieu et mon droit was the inspiration for The Beatles' joke motto Duit on Mon Dei, later adopted as an album title by Harry Nilsson. The former phrase was also used on Hong Kong's bank notes from 1987.