Maleva: The way you walked was thorny, through no fault of your own, but as the rain enters the soil, the river enters the sea, so tears run to a predestined end. Your suffering is over, Bela my son. Now you will find peace.
Maleva: You are not frightened, are you, Sir John?
Sir John Talbot: Frightened, of what?
Maleva: Of the night.
Sir John Talbot: Rubbish. You startled me.
Maleva: Don't be startled, Sir John. You have the silver cane for protection.
Sir John Talbot: Who are you?
Maleva: Hasn't your son told you?
Sir John Talbot: You're the gypsy that's been filling his mind with this werewolf nonsense.
Frank Andrews: I couldn't take my eyes off that walking stick of his.
Larry Talbot: It isn't a wolf... it's a werewolf.
Col. Paul Montford, chief constable: Just imagine having a stuffed werewolf staring at you from the wall.
Doctor Lloyd: I believe a man lost in the mazes of his own mind may imagine that he's anything.
Larry Talbot: Oh its all Greek to me.
Sir John Talbot: Well, it is Greek.
Sir John Talbot: Yes, that's the sign of the werewolf.
Larry Talbot: That's just a legend though, isn't it?
Sir John Talbot: Yes, but like most legends, it must have some basis in fact. It's probably an ancient explanation of the dual personality in each of us. How does it go?"Even a man who is pure in heart and says his prayers by night may become a wolf when the wolfbane blooms and Autumn moon is bright."
Sir John Talbot: All astronomers are amateurs. When it comes to the heavens, there's only one professional.
Larry Talbot: That's what she said.
Sir John Talbot: You can't run away.
Larry Talbot: That's it! That's what she said.
Sir John Talbot: Who?
Larry Talbot: The gypsy woman.
Sir John Talbot: Gypsy woman? Now we're getting down to it. She's been filling your mind with this gibberish. This talk of werewolves and pentagrams. You're not a child Larry, you're a grown man and you believe in the superstitions of a Gypsy woman.
Answer: Werewolves as a concept date back many years - this film originated many of the current conventions though, so the simple answer to your question is "the writers of this film". See the Wikipedia for more info - http://en.wikipedia.org/wiki/Werewolf.