Commonly used by Shakespeare, and dating back further than that, its usage is usually literary and archaic but always humorous. It has some properties of an English adverb and some of an English verb. However, it largely defies conventional linguistic analysis; and that seems to be the point: The humour derives from the fact that it's ungrammatical, and a character, who may be comedic or serious, attempting some deep-thinking is actually at least on some levels demonstrating stupidity by making a crass linguistic error.
- "Methinks I see thee, now thou art below, As one dead in the bottom of a tomb." (Juliet in Romeo and Juliet, Act 3 scene 5)
- "The lady doth protest too much, methinks" Queen Gertrude in Hamlet Act 3 Scene 2.
- "Methinks I have a great desire to a bottle of hay: good hay, sweet hay, hath no fellow." (Bottom in A Midsummer Night's Dream, Act 4 Scene 1)