joevitus said: "That probably was the question. It seems like I read somewhere that the title was taken from the children's song "Row, Row, Row Your Boat," though I'm not entirely sure that's accurate, as the song has no line with thatphrase.I'm guessing if the songis indeed the inspiration,Kaufman and Hart were making an ironic comparison between "Life if but a dream" and the far from idylliclivestheir protagonists end up living."
If it came from a song, it's probably "Goodnight, Ladies," which is a folk song that includes the lyric (and later inspired a WB Merrie Melodie by the same name as the play/musical but is unrelated to either).