I had no idea, so I checked wikipedia.

A wolf in sheep’s clothing is an idiom from Jesus’s Sermon on the Mount as narrated in the Gospel of Matthew.

That would be the earliest recording and after there are various versions involving a wolf and deception created every few centuries.

Cry wolf is apparently from Aesop, before he went on a journey to find the One Piece. Oh sorry, my mistake, I misremembered the name…

Same reason atheists say “god damn it” etc

It’s cultural/societal.

Well, ever hear the story of the boy who cried wolf? That’s the origin of that one. And, as someone else already covered, the wolf in sheep’s clothing is biblical in origin, though it has been through some other usages over the years.

Your be amazed how many of Aesop’s fables are still in the consciousness of people that have never directly read them just because they’re so deeply engrained into culture.