renal (adj.) Look up renal at Dictionary.com
1650s, from French rénal and directly from Late Latin renalis "of or belonging to kidneys," from Latin ren (plural renes) "kidneys," a word of of uncertain etymology, with possible cognates in Old Irish aru "kidney, gland," Welsh arenn "kidney, testicle," Hittite hah(ha)ari "lung(s), midriff." Also possibly related are Old Prussian straunay, Lithuanian strenos "loins," Latvian streina "loins." "The semantic shift from 'loins' to 'kidneys' is quite conceivable" [de Vaan].