Etymology of 羊膜 (youmaku)

I was intrigued by the combination of kanjis in 羊膜, made up by 羊 (sheep) and 膜 (membrane) to mean amnion. After a little bit of googling, this is what I found:

胎児を包む膜のことを羊膜、そのなかの液体を羊水という。

遊牧民が神にたいする供儀として、羊（妊娠羊）を犠牲にして腹を切り開いたところ、胎児が液体を満たした袋に包まれていることを見つけたことから、つけられた名前だ。

羊膜は英語でamnionという。これはラテン語のAmmon（古代エジプトの太陽神アモンのことで、羊の角を生やした神）に由来する。

Which can be translated as: The amnion is the membrane that envelops the fetus, where you find the amniotic fluid.
Nomadic peoples revered the gods by celebrating a festival in which they gutted a sheep, especially a pregnant one, and the bag which they found inside the animal was filled with a fluid around the embryo, from which it got its name.

Youmaku is translated as amnion in English, which derives from Latin Ammon (the name of the ancient Egyptian sun god, the ram with curved horns.

And this is what I found concerning the origin of amnion.