muck (n.)

"soft mixture, mass of ingredients beaten or stirred together," late Old English *masc (in masc-wyrt "mash-wort, infused malt"), from Proto-Germanic *maisk- (source also of Swedish mäsk "grains for pigs," German Maisch "crushed grapes, infused malt," Old English meox "dung, filth"), possibly from PIE root *meik- "to mix."

Originally a word in brewing; general sense of "anything reduced to a soft pulpy consistency" is recorded from 1590s, as is the figurative sense "confused mixture, muddle." Short for mashed potatoes it is attested from 1904.

mid-14c., midding, "dunghill, muck heap," a word of Scandinavian origin; compare Danish mødding, from møg "muck" (see muck (n.)) + dynge "heap of dung" (see dung). Modern archaeological sense of "prehistoric place for disposing of kitchen refuse, ashes, etc." is 19c., from Danish excavations.

also muckraker, c. 1600, "one who rakes muck" (earliest use is in a figurative sense: "a miser"), from muck-rake "rake for scraping muck or filth" (mid-14c.), from muck (n.) + rake (n.). The figurative meaning "one who inquires into and publishes scandal and allegations of corruption among political and business leaders" was popularized 1906 in speech by President Theodore Roosevelt, in reference to the "man ... with a Muckrake in his hand" in Bunyan's "Pilgrim's Progress" (1684) who seeks worldly gain by raking filth.

The men with the muck-rakes are often indispensable to the well-being of society, but only if they know when to stop raking the muck. [T. Roosevelt, quoted in "Cincinnati Enquirer," April 15, 1906.]

Muck-rake (n.) in sense "person who hunts scandal" is attested from 1872. To muck-rake (v.) in the literal sense is from 1879; figuratively from 1910. Related: Muck-raking.