Guy Fawkes used the first name Guido before becoming known as Guy Fawkes on Bonfire Night.
He was born in York in 1570 and was baptised Guido Fawkes. After converting to Catholicism, he travelled to continental Europe and served in the Spanish Netherlands, where the name Guido was used in records.
The English form “Guy” became associated with him later. It was also reinforced by the annual commemoration of the failed 1605 Gunpowder Plot, when effigies called “Guys” came to be burned on 5 November.
A common mix-up is treating Guido as a nickname invented after his arrest. It was his baptismal first name, while Fawkes was his surname. His religious conversion and military experience helped make him useful to the conspirators, who placed him in charge of the gunpowder beneath the House of Lords.