moulder

Etymology 1

Verbal use of mould

verb

1. (British spelling, transitive, intransitive) To decay or rot.
   [Time's] gradual touch / Has moulder'd into beauty many a tower. 1772–1782, William Mason, The English Garden
   John Brown's body lies a-mouldering in the grave, but his soul goes marching on! c. 1855, John Brown’s Body
   Today the trackbed moulders, although Lancashire council reports that it's largely intact to around 1.5 miles south of Fleetwood. January 12 2022, Philip Haigh, “Okehampton should be the start of railway restoration”, in RAIL, number 948, page 50

Etymology 2

mould + -er

noun

1. A person who moulds dough into loaves.
2. Anyone who moulds or shapes things, including in a mould.
   It was, however, most interesting work, and the moulders themselves were a decent crowd, never tired of making jokes about themselves such as the hoary one that moulders did not live long, which however ran counter to the other one that no germs could live in a foundry—the atmosphere was too foul. 1944 November and December, A Former Pupil, “Some Memories of Crewe Works—II”, in Railway Magazine, page 342
3. A machine used for moulding.