rognon

from Latin ren (kidney) becoming rēniōn, rēniōnem in popular Latin, roignon, reignon ("human or animal kidney") in Old French. In the seventeenth century, due to the re-borrowing of rēn from Latin and its medical use, the word becomes specialized in the veterinary and butcher's sense of "animal kidneys" and also takes on the meaning of "testicle of certain animals" by analogy of shape.