have a bee in (one's) bonnet

To talk incessantly about something one thinks is important (often in spite of others' disinterest). Ever since the blizzard last year, Dad has had a bee in his bonnet about moving to a warmer climate It seems that Mike still has a bee in his bonnet over the criticism he got in the staff meeting. A: "Harry's still out there planting?" B: "Yes! He's had a bee in his bonnet all week about growing his own vegetables."

bee in one's bonnet, to have a

To have a strange fixation about something; to have an eccentric idea or fantasy. A version of the term appears in Robert Herrick’s “Mad Maid’s Song” (ca. 1648): “. . . the bee which bore my love away, I’ll seek him in your bonnet brave.” Allegedly the expression stems from the analogy of a bee buzzing inside one’s hat to a peculiar idea in one’s head. It has been a cliché since the eighteenth century. Lest one think it is obsolete, it appeared in a 2004 murder mystery: “By the way, what bee got into your bonnet at the meeting? Bailey had been pretty cooperative” (David Baldacci, Hour Game).