Over the moon
Over the moon means wildly excited or elated, the source is the anonymous nursery rhyme, Hey Diddle Diddle, which dates from the late 1700s, where the cow jumped over the moon and made the little dog laugh. There is evidence, however, that Hey Diddle Diddle itself was the name of a dance first cited in 1569, according to the Oxford Dictionary of Nursery Rhymes. Ever since the nursery rhyme became popular, people have been jumping over the moon for joy, as one of the earliest citations proves. Charles Molloy in his play The Coquet or The English Chevalier (1718) wrote, “Tis he, I know him now: I shall jump over the moon for joy!” 'Jumping for joy' and being 'over the moon' have become two separate idioms for expressing happiness, both deriving from the original nursery rhyme.