A fais do-do is a Cajun dance party, originating before World War II.
According to Mark Humphrey, the parties were named for "the gentle command ('go to sleep') young mothers offered bawling infants." He quotes early Cajun musician Edwin Duhon of the Hackberry Ramblers:
"Do-do" itself is a shortening of the French verb dormir (to sleep), used primarily in speaking to small children. The phrase is comparable to the American English "beddy-bye",, and is embodied in an old French lullaby, a song sung to children when putting them down for the night. Its existence in Cajun culture as a source for dances, or bands, comes from an affection for the term itself.
Occurrences include the following:
"Fais do" (1998–2010)
"Mama Lisa’s World :Children's Songs and Nursery Rhymes", Lisa Yannucci (2010)