- noun an organ in vertebrates that regulates and filters waste for excretion
- The internal organ of an animal which filters out breakdown products of metabolism from the blood and delivers them in water solution to the bladder. The main bulk is a uniform brownish-red tissue arranged around blood vessels and tubes. Generally prized as tender and tasty offal. The kidneys of smaller animals are grilled or fried after removing the hard core, outer membrane and fat. The kidneys of larger animals are generally stewed.
- noun either of two organs situated in the lower part of the back on either side of the spine behind the abdomen, whose function is to maintain the usual concentrations of the main constituents of blood, passing the waste matter into the urine.
- noun this organ used as food
Origin & History of “kidney”
The origins of kidney are a matter of guesswork rather than certain knowledge. Probably the most widely accepted theory is that the -ey element represents ey, the middle English word for ‘egg’, in allusion to the shape of the kidneys. The first syllable is more problematical, but one possible source is Old English cwith ‘womb’ or the related Old Norse kvithr ‘belly, womb’, in which case kidney would mean etymologically ‘belly-egg’.