Kidney
wiktionary
From Middle English kednei, kidenei, from earlier kidnēre, kidenēre(“kidney”), of obscure origin and formation. Probably a compound consisting of Middle English *kid, *quid(“belly, womb”), from Old English cwiþ, cwiþa(“belly, womb, stomach”) + Middle English nēre(“kidney”), from Old English *nēora(“kidney”), from Proto-Germanic *neurô(“kidney”), from Proto-Indo-European *negʷʰr-(“kidney”). If so, then related to Scots nere, neir(“kidney”), Saterland Frisian Njuure(“kidney”), Dutch nier(“kidney”), German Niere(“kidney”), Danish nyre(“kidney”), Norwegian nyre(“kidney”), Swedish njure(“kidney”), Ancient Greek νεφρός(nephrós).
Alternate etymology traces the first element to Old English cēod, codd(“sack, scrotum”), from Proto-Germanic *keudō(“sack”) as the terms for testicle and kidney were often interchangeable in Germanic (compare Old High German nioro(“kidney", also "testicle”), Old Swedish vig-niauri(“testicle”). More at codpiece.
etymonline
kidney (n.)
early 14c., kidenere, a word of unknown origin, perhaps a compound of Old English cwið "womb" (see chitterlings) + ey "egg" (see egg (n.)) in reference to the shape of the organ. Figurative sense of "temperament" is from 1550s. Kidney-bean is from 1540s, so called for its shape.
