From Middle English kednei, kidenei, from earlier kidnēre, kidenēre, of obscure origin and formation.

Alternate etymology traces the first element to Old English cēod, codd, from Proto-Germanic *keudō as the terms for testicle and kidney were often interchangeable in Germanic (compare Old High German nioro, gmq-osw vigniauri).

• (British, Canada) IPA: /ˈkɪdni/

kidney (plural kidneys)

1. An organ in the body that filters the blood, producing urine.
2. This organ (of an animal) cooked as food.
3. (figuratively, dated) Constitution, temperament, nature, type, character, disposition. (usually used of people)
   • c. 1597 (date written), William Shakespeare, “The Merry Wiues of Windsor”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC ↗, [Act V, (please specify the scene number in lowercase Roman numerals)]:

     […] think of that, – a man of my kidney, – think of that, […]

   • 1692, Roger L'Estrange, “ (please specify the fable number.) (please specify the name of the fable.)”, in Fables, of Æsop and Other Eminent Mythologists: […], London: […] R[ichard] Sare, […], →OCLC ↗:

     Millions in the World of this Man's Kidney

   • 30th June, 1788, Robert Burns, letter to Mr Robert Ainslie

     Your poets, spendthrifts, and other fools of that kidney, pretend, forsooth, to crack their jokes on prudence.

4. (obsolete, slang) A waiter.

• rein
• nephros
• ren

• French: rein
• German: Niere
• Italian: rene
• Portuguese: rim
• Russian: по́чка
• Spanish: riñón

• French: rognon
• Italian: rognone
• Portuguese: rim
• Russian: по́чки

From a mistranslation of Irish Ó Dubháin (directly rendered in English as Duane), a personal name from a diminutive of dubh ("black").

1. Surname.