Orig. a person who worked with lead, after the Latin plumbum = lead. Indeed English plumbers were in great demand on the continent: English lead roofed both Clairvaux and Rouen cathedrals in the 12c. However, lead was also used for rain-pipes and guttering, and the Romans had used it for carrying fresh water. The abbey at Bury St Edmunds had a two-mile-long system of lead pipes for its water supply. In 1091, the bishop of Coutances requested an English plumber be sent to mend the roof of his *cathedral which had been damaged by lightning. One Brismet, the plumber, was sent to help. -
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.