Methinks my mind is blown

DailyWritingTips.com is a fun website that sends me daily tidbits about writing. Mostly it's mundane stuff that only the wordiest of nerds care much about, but now and then you get a taste of something loftier - this week it was Hamlet.
We all know the quotation from Hamlet - "Methinks the lady doth protest too much." It's an expression people use to mean that someone's suspiciously eager to deny something, and therefore probably lying.
Except the line isn't "Methinks the lady doth protest too much," and that furthermore, the expression doesn't mean what people think at all.
The line comes during the Mousetrap scene - the one in which Hamlet hires some actors to perform a play that essentially calls his uncle a murderer and his mom a whore. During the play, the lady playing the queen gives a speech about how great her husband is, and how she'd never ever get married to anyone else if her husband died - laying it on thick. Hamlet, because his barely passive aggression wasn't obvious enough, asks his mom what she thinks of that, and she replies "The lady protests too much, methinks."
So big deal, not a huge misquote. What's huge is the meanings of the words in the quotation. Methinks doesn't mean I think, it means it seems like. And it turns out the meaning of the word protest has shifted since Shakespeare's day. Back then, it meant to proclaim or to promise. So the queen isn't saying "I think she's lying," she's saying "it seems like she is promising more than what's reasonable."
The shift in meaning of protest, according to Etymonline.com, probably comes from the common expression protest one's innocence; the phrase started out meaning "to proclaim you're not guilty" but shifted to mean "to deny your guilt."

Super-cool Hamlet fact: poor Yorick up there isn't a prop - the late Andre Tchaikovsky plays opposite the great David Tennant in this scene - the pianist and composer died in 1982, leaving his head to the Royal Shakespeare Company in the hopes he'd get to play the dead dude one day. The director of the Tennant version of Hamlet says, "You can't hold a real human skull in your hand and not be moved by the realisation that your own skull sits just beneath your skin, that you will be reduced to that state at some stage."
If you haven't seen Tennant's Hamlet, you absolutely should.