plodder
A person who, or animal that, plods.
Grave old plodders, gay young friskers […]
Brown rats, black rats, grey rats, tawny rats,A person who works slowly, making a great effort with little result; a person who studies laboriously.
That will not be deep-search’d with saucy looks: Small have continual plodders ever won Save base authority from others' books
Study is like the heaven’s glorious sunA machine for extruding soap, margarine, etc. through a die plate so it can be cut into billets.
From the mill the soap passes into the hopper of the plodder. This machine feeds it automatically into a compartment where it is subjected to an enormous pressure, forming it again into a compact mass.
Where it comes from
From Middle English plodder, equivalent to plod + -er.
Adapted from the Wiktionary entry plodder (CC BY-SA 4.0).