Amnion
/ˈæm.ni.ən/noun
The thin membrane that surrounds the embryo or fetus in mammals, reptiles, and birds.
Did you know?Amnion comes from Greek amnion, originally the name of a lamb’s pelt or sacrificial bowl, so the word’s history is far older and more ritual-charged than modern medicine suggests.
Etymological Timeline
Proto-Indo-European
PIE
*h₂em-
“Likely a root meaning "to fit together, join" or related to wool/covering in the broader etymological background of Greek forms; the exact prehistory is uncertain.”
Ancient Greek
Greek
ἀμνίον (amnion)
“A small bowl or basin; also a lamb’s pelt or the membrane enclosing the fetus.”
Late Greek / Hellenistic
Greek
ἀμνίον
“Used in anatomical and medical contexts for the fetal membrane.”
Late Latin
Latin
amnion
“A medical term adopted from Greek for the membrane around the embryo.”
Middle English
English
amnyon / amnion
“Anatomical term for the membrane enclosing the unborn young.”
Modern English
English
amnion
“The innermost membrane surrounding the embryo or fetus in amniotes.”