cotyledon

Etymology

From Latin cotylēdōn, from Ancient Greek κοτυληδών (kotulēdṓn, “cup-shaped cavity”), from κοτύλη (kotúlē, “cup”).

noun

1. (physiology) Each of the patches of villi on the foetal chorion in the placenta of ruminants and some other mammals.
   Forced to apply animal findings to humans, his human womb also had cotyledons like a dog's. 1997, Roy Porter, The Greatest Benefit to Mankind, Folio Society, published 2016, page 72
2. (botany) The leaf of the embryo of a seed-bearing plant; after germination it becomes the first leaves of the seedling.