"to squeeze flat," 1879, from pancake (n.). Later, of aircraft, "to fall flat" (1911), with figurative extension. Related: Pancaked; pancaking.

"fine soft mud or slime," Old English wase "soft mud, mire," from Proto-Germanic *waison (source also of Old Saxon waso "wet ground, mire," Old Norse veisa "pond of stagnant water"), probably from a PIE root meaning "wet." Modern spelling is from mid-1500s.

late 13c., in place names, "abounding in or covered with mud," from mud + -y (2). Meaning "not clear or pure in color" is from 1580s; extended to sounds by 1960s. Big Muddy as a nickname for the Missouri or Mississippi river is attested by 1825. Related: Muddily; muddiness.

1670s of plants, "part of the ovary of flowering plants which bears the ovules," 1690s of mammals, "organ of attachment of a vertebrate embryo or fetus to the wall of the uterus or womb of the female," from Modern Latin placenta uterina "uterine cake" (so called 16c. by Italian anatomist Realdo Colombo), from Latin placenta "a cake, flat cake," from Greek plakoenta, accusative of plakoeis "flat," from plax "flat, flat land, surface, plate," from PIE root *plak- (1) "to be flat." So called from the shape.

1590s, "destroy the clarity of" (a transferred sense); literal sense ("to bathe in mud") is from c. 1600; perhaps frequentative formation from mud, or from Dutch moddelen "to make (water) muddy," from the same Proto-Germanic source. Sense of "to make muddy" is from 1670s; that of "make confused, bewilder" is recorded by 1680s. Meaning "to bungle" is from 1885. Related: Muddled; muddling.

"flat piece of ground," mid-15c. (mid-13c. in surnames), a variant of plot (n.) assimilated to Middle English plat (adj.) "flat," which is from Old French plat "flat, stretched out" (see plateau (n.)). See OED plat sb.3 for full explanation.

"lying in or otherwise related to a plane, flat," 1850, from Latin planaris "level, flat," from planum "plane" (from PIE root *pele- (2) "flat; to spread"). An earlier word in the same sense was planary (1660s).

also *plāk-, Proto-Indo-European root meaning "to be flat;" extension of root *pele- (2) "flat; to spread."

It forms all or part of: flag (n.2) "flat stone for paving;" flagstone; flake (n.) "thin flat piece,; flaw; floe; fluke (n.3) "flatfish;" placenta; plagal; plagiarism; plagio-; planchet; plank.

It is the hypothetical source of/evidence for its existence is provided by: Greek plakoeis "flat," plax "level surface, anything flat;" Lettish plakt "to become flat;" Old Norse flaga "layer of earth," Norwegian flag "open sea," Old English floh "piece of stone, fragment," Old High German fluoh "cliff."

mid-15c., slori, "thin mud, slime, semi-fluid mix of water and earth or clay," probably related to Middle English sloor "thin or fluid mud" (see slur (n.)). Slori also turns up as a nickname c. 1200, perhaps "dirty or lazy person."

"thin flat piece of snow; a particle," early 14c., also flauke, flagge, which is of uncertain origin, possibly from Old English *flacca "flakes of snow," or from cognate Old Norse flak "flat piece," from Proto-Germanic *flakaz (source also of Middle Dutch vlac, Dutch vlak "flat, level," Middle High German vlach, German Flocke "flake"); from PIE root *plak- (1) "to be flat." From late 14c. as "a speck, a spot."