The last injunction of Charles I., on the scaffold, to Bishop Juxon. A probable solution of this mysterious word is given in Notes and Queries (February 24th, 1894, p. 144). The substance is this: Charles, who was really at heart a Catholic, felt persuaded that his misfortunes were a divine visitation on him for retaining the church property confiscated by Henry VIII., and made a vow that if God would restore him to the throne, he would restore this property to the Church. This vow may be seen in the British Museum. His injunction to the bishop was to remember this vow, and enjoin his son Charles to carry it out. Charles II., however, wanted all the money he could get, and therefore the church lands were never restored.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Remember from Fact Monster: