c.1300, "food for one meal, pottage," from Old French mes "portion of food, course at dinner," from Late Latin missus "course at dinner," literally "a placing, a putting (on a table, etc.)," from past participle of mittere "to put, place," in classical Latin "to send, let go" (see mission).Meaning "communal eating place" (especially a military one) is first attested 1530s, from earlier sense of "company of persons eating together" (early 15c.), originally a group of four. Sense of "mixed food," especially for animals, (1738) led to contemptuous use for "jumble, mixed mass" (1828) and figurative sense of "state of confusion" (1834), as well as "condition of untidiness" (1851). General use for "a quantity" of anything is attested by 1830. Meaning "excrement" (of animals) is from 1903.

late 14c., "serve up in portions," from mess, n.. Meaning "take one's meals" is from 1701; that of "make a mess" is from 1853. Related: Messed; messing. To mess with "interfere, get involved" is from 1903; mess up "make a mistake, get in trouble" is from 1933 (earlier "make a mess of," 1909), both originally American English colloquial.