 The song is a turning point in the plotline of the musical.Professor Higgins and Colonel Pickering have been drilling Eliza Doolittle incessantly with speech exercises, trying to break her Cockney accent speech pattern.The key lyric in the song is "The rain in Spain stays mainly in the plain", which contains five words that a Cockney would pronounce with or  – more like "eye" than the Received Pronunciation diphthong .