In the society of the members he assumed the name of "Isaac Bickerstaff," and later of "Gawin Douglas," the latter partly in memory of his maternal grandfather Douglas of Muthill (Perthshire), and partly to give point to his boast that he was a "poet sprung from a Douglas loin."
This notice attracted Swift's attention, and in January 1708 he issued predictions for the ensuing year by Isaac Bickerstaff, written to prevent the people of England being imposed upon by vulgar almanac makers.
The poor man was obliged to issue a special almanac to assure his clients and the public that he was not dead: he was fatuous enough to add that he was not only alive at the time of writing, but that he was also demonstrably alive on the day when the knave Bickerstaff (a name borrowed by Swift from a sign in Long Acre) asserted that he died of fever.
This elicited Swift's most amusing Vindication of Isaac Bickerstaff Esq.
Lecky; Tale of a Tub; Battle of the Books; Critical Essay upon the Faculties of the Mind; The Bickerstaff Pamphlets, &c., ed.