What Does "Fais Do-Do" Mean?
Well, according to Wikipedia...
Fais do-do is a name for 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 crying infants." He quotes early Cajun musician Edwin Duhon of the Hackberry Ramblers, "She'd go to the cry room, give the baby a nipple and say, 'Fais do-do.' She'd want the baby to go to sleep fast, 'cause she's worried about her husband dancing with somebody else out there."
'Do-do' itself is a shortening of the French verb dormir (to sleep), used primarily in speaking to small children. Comparable to the American English "night-night", it is still commonly used by French-speaking people.
Wikipedia contributors. "Fais do-do." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 9 Feb. 2011. Web. 11 May. 2011.
Also see Edmond Boudreaux' Faire Dodo
Origin
Louisiana French; French: go to sleep! ( fais 2nd singular imperative of faire to do, make; dodo nursery word for “sleep,” probably based on dod ( el ) iner to nod, dandle (a child), influenced by dormir to sleep
"fais-dodo." Dictionary.com Unabridged. Random House, Inc. 11 May. 2011.