"soft mixture," late Old English *masc (in masc-wyrt "mash-wort, infused malt"), from Proto-Germanic *maisk- (cognates: Swedish mäsk "grains for pigs," German Maisch "crushed grapes, infused malt," Old English meox "dung, filth"), from PIE *meik- "to mix" (see mix, v.). 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.

Old English mæscan, "to mix with hot water," from same root as mash, n.. Meaning "to beat into a soft mass" is mid-13c. Related: Mashed; mashing. For romantic sense, see masher.