Definition of "plodder"

Brown rats, black rats, grey rats, tawny rats,Grave old plodders, gay young friskers […]

1842, Robert Browning, The Pied Piper of Hamelin, London: Frederick Warne, published 1888, page 18

Study is like the heaven’s glorious sunThat will not be deep-search’d with saucy looks:Small have continual plodders ever wonSave base authority from others' books

c. 1595–1596 (date written), William Shakespeare, “Loues Labour’s Lost”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene i]

What an indefatigable plodder you are to get those papers ready so soon, and an unmerciful man besides to make me go over them to-night.

1899, Pansy (pseudonym of Isabella Macdonald Alden), Three People, Boston: Lothrop, Lee & Shepard, Chapter 21, p. 271

Throughout my life […] I have been fortified in the conclusion that it is much more important for a young man to be a worker, even though not brilliant, than to be brilliant and not a worker. As one looks back at some companions who attended lectures, and follows the records of their lives, one is strengthened in this belief because the facts show that the steady plodders have gone further than have some of those brilliant lads of other days.

1939, Robert James Manion, Life is an Adventure‎, Toronto: Ryerson Press, Part Two, II, p. 43

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.

1893, Henry Gathmann, American Soaps, page 258