"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.
also mish-mash, late 15c., mysse-masche, probably an imitative reduplication of mash (n.). Compare German mischmasch, Danish miskmask.
"kind of porridge; meal boiled in water or milk until it forms a thick, soft mass," 1670s, in the American colonies, a variant of mash (n.) "soft mixture." Meaning "anything soft and thick" is attested from 1824.
mid-13c., muk, "animal or human excrement; 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," which is perhaps related to Old English meox "dung, filth" (see mash (n.)). Meaning "unclean matter generally" is from c. 1300; that of "wet, slimy mess" is by 1766. Muck-sweat "profuse sweat" is attested from 1690s.
c. 1500, "thing that mashes," agent noun from mash (v.). Meaning "would-be lady-killer, one whose dress or manners are such as to impress strongly the fancy of susceptible young women" is by 1875, American English, perhaps in use from 1860, probably from mash (v.) on notion either of "pressing one's attentions" or "crushing someone else's emotions" (compare crush (n.)).
He was, to use a Western expression, a 'regular heart-smasher among the women;' and it may not be improper to state, just here, that no one had a more exalted opinion of his capabilities in that line than the aforesaid 'Jo' himself. [Harper's New Monthly Magazine, March 1861]
He had a weakness to be considered a regular masher of female hearts and a very wicked young man with the fair sex generally, but there was not a well-authenticated instance of his ever having broken a heart in his life, nor likely to be one. [Gilbert A. Pierce, "Zachariah, The Congressman," Chicago, 1880]
Also in use in late 19c were mash (n.) "a romantic fixation, a crush" (1882); mash (v.) "excite sentimental admiration" (1882); mash-note "love letter" (1890).
also *meig-, Proto-Indo-European root meaning "to mix."
It forms all or part of: admix; admixture; immiscible; mash; meddle; medley; melange; melee; mestizo; metis; miscegenation; miscellaneous; miscible; mix; mixo-; mixture; mustang; pell-mell; promiscuous.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit misrah "mixed;" Greek misgein, mignynai "to mix, mix up, mingle; to join, bring together; join (battle); make acquainted with;" Old Church Slavonic mešo, mesiti "to mix," Russian meshat, Lithuanian maišau, maišyti "to mix, mingle," Welsh mysgu "to mix."