A: Has John won the lottery? He’s been humming all morning.

    B: He met an actress and is head over heels in love.

    Note: This idiom means very excited and/or joyful, especially when in love. When first coined it wasn’t used that way though and referred exclusively to being temporarily the wrong way up. It is one of many similar phrases that we use to describe things that are not in their usual state, like upside-down, topsy-turvy, topple up tail. The first mention of love comes after the time that the phrase had crossed the Atlantic to the United States. Here is an example from the Indiana newspaper The Lebanon Patriot, June 1833, and the lack of quotation marks or explanation suggests that the expression was in common usage by that time: About 10 years ago Lotta fell head over heels in love with a young Philadelphian of excellent family.