What the dickens: Meaning Then
What was Big Willy Shakes going for?
Look. Mistress Page and her bestie Mistress Ford might be faithful, but we're not saying our housewives are a couple of naive prudes or anything. They speak pretty candidly to each other about sex and they're not afraid to crack a mildly dirty joke now and then.
In fact, Mistress Page is using a euphemism right here. She might say "what the dickens" but what she is really saying is just a substitute for something stronger. It's called a minced oath. This is when someone uses one phrase to avoid swearing.
It's like saying "Jiminy Cricket!" or "for Pete's sake" instead of words your mother wouldn't approve of. Mistress Page might be feigning surprise here, but her minced oath sure is real.
In Shakespeare's day, "dickens" was a euphuism for the Devil. Kind of like people say "gosh" instead of "God" now to skip on a stronger phrase. We told you Mistress Page was feisty.