Bee

[jasminekitty]

what does bee in someone's bonnet mean

[jak108]

Having a bee in one's bonnet means that something is really annoying them. A bonnet is a ladies hat.

[Quizmonster]

Click http://www.bartleby.com/101/268.html and a link will take you to a web-page with Robert Herrick's 17th century poem 'A Mad Maid's Song'. This is, supposedly, where the idea that having a bee in your bonnet is a sort of madness comes from.