“The lady doth protest too much, methinks,” says Queen Gertrude in Hamlet, watching a play wherein a woman professes, in the most fulsome terms, utter devotion to her husband the king, two minutes before the king’s brother will poison him by pouring poison into his ear, and four minutes before that devoted woman will marry her brother-in-law. Oops!
What does the word mean? And why is it methinks? I imagine a Huron queen watching the same play, and struggling with the foreign language. “Me think the lady doth protest too much.”
It’s methinks because it’s a compound of the dative pronoun me and an impersonal verb, thinks. That verb isn’t what you think it is. The Old English verb for think was thencan: German denken. But what if something seems funny to you? What if it makes you think? That causative verb had a different vowel in it: it was thyncan: German duenken. The Germans don’t use that verb much these days, but when they did use it, it was just as in olden English: Mir duenkt es graesslich, It seems ghastly to me; methinks it ghastly. In Old English the phrase was me thyncath: It seems to me.
So that is what the s is doing there. It’s just the third person singular ending on the impersonal verb: it seems. Methinks = it seems to me. Latin speakers did the same thing with their verb videri, to be seen. It also means it seems: visus sum = it seemed to me. Cf. English: it looked that way to me.