The term Achilles’ heel has an apostrophe, because it’s a reference to the heel that belonged to the ancient Greek hero Achilles. Therefore, by the transitive properties of apostrophes, when we talk about something being our Achilles’ heel, that something does not actually belong to us. It belongs to Achilles. Even though that guy has been dead for like, forever.
And given that Achilles allowed his own Achilles’ heel to be shot by an arrow, I really don’t think that we should be trusting this Achilles guy with all of our Achilles’ heels!
Seriously, we’re really vulnerable here – this is an area of weakness that someone may exploit.