I've tagged this one ABUNAI, because it's often used ironically - more like 'bitch'.
To make things even more complicated, the rude version is often written as '阿魔' rather than 尼, I guess to not be blasphemous. Even though the origin of the word is 尼! But who cares - chances are you'll mostly encounter the rude version in conversation anyway ('このあま！' or ’このあまっこ！’). So forget I said anything about 阿魔. . .
It's the corpse of a nun who got poisoned-darted in the heel, all Achilles style. Weird.
Nuns wear high-HEELS under their gowns.
The heels get WET from the MUD.
To beat a baseball team, you must kick NINE butts!