Whilst doing her own research on EEBO, your trustie RA has found evidence that Batman did indeed exist in Early Modern England. Click HERE.
Bartholomaeus, Anglicus, 13th cent. Batman Vppon Bartholome His Booke De Proprietatibus Rerum, Newly Corrected, Enlarged and Amended: With Such Additions as Are Requisite, Vnto Euery Seuerall Booke: Taken Foorth of the Most Approued Authors, the like Heretofore Not Translated in English. Profitable for All Estates, as Well for the Benefite of the Mind as the Bodie. 1582. Edited by Stephen Batman d. Early English Books, 1475-1640 / 196:03. London: Thomas East, dwelling by Paules wharfe, 1582.