muck: [13] The original meaning of muck is ‘excrement’; the more general ‘dirt’ is a 14thcentury development. It goes back to a prehistoric Germanic *muk-, *meuk- ‘soft’. This was also the source of Danish møg ‘dung’ (which provides the first syllable of midden [14], a borrowing from the ancestor of Danish mødding, literally ‘dung-heap’). The same Germanic base lies behind English meek [12], whose immediate Old Norse antecedent mjúkr meant ‘soft, pliant’ – leading on in due course to English ‘submissive’. => meek, midden
muck (n.)
mid-13c., "cow dung and vegetable matter spread as manure," from a Scandinavian source such as Old Norse myki, mykr "cow dung," Danish møg; from Proto-Germanic *muk-, *meuk- "soft." Meaning "unclean matter generally" is from c. 1300. Muck-sweat first attested 1690s.
muck (v.)
late 14c., "to dig in the ground," also "to remove manure," early 15c., "to spread manure, cover with muck," from muck (n.). Meaning "to make dirty" is from 1832; in the figurative sense, "to make a mess of," it is from 1886; to muck about "mess around" is from 1856. Related: Mucked; mucking.