plumb ‧ er /ˈplʌmə $ -ər/ BrE AmE noun [countable]
[ Date: 1300-1400 ; Language: Old French ; Origin: plommier 'worker in lead' , from Latin plumbarius , from plumbus 'lead' ; because water pipes were originally made of lead ]
someone whose job is to repair water pipes, baths, toilets etc