How did the phrase " Speak of the devil" come to be ?

it was originaly "Speak of the devil, and the devil shall come." But it was made shorter to "speak of the devil"

Im not 100% but i think it might have been originated from a story

*shrugs*

An old superstition was that if you talked about the devil, he would come to you.

So, if you are talking about somebody and they walk into the room, you say "Speak of the devil..."

Edit- Thanks Joah, I couldn't, for the life of me, remember what the original saying was, just knew the gist of it. You get props for that one.

Add the first answer to the second one, and you will get the answer to your question.