Why do two verbs mean “to sleep”: coucher and dormir? What’s the difference? Does it switch for different verb usages, like past-perfect and future-conditional and all that good stuff? Or, are they synonmys? Or, does one have a different connotation than the other?
Being the French student par excellence, NOT! I can only advise: One should best experience French as a dressing! 
LoL!
I read Coucher in the sense of to go to bed, usually in order to sleep. Dormir is the state of sleeping or being asleep.
I came in to say this.
Which is why “Voulez-vous coucher avec moi ce soir?” is a sexy question, while “Voulez-vous dormir avec moi ce soir?” is not.
Speed bumps in some French-speaking countries are called le gendarme couche, which I think is an excellent descriptive.
coucher= to lie (down)
dormir= to sleep
Simple as that. You can be couché and not sleep.
It’s said in the formal second person, with vous. Implying that the speaker and the invitee are strangers or on different levels of status. (Contrasted with inviting a close acquaintance to go to bed with you, when you’d use the informal veux-tu.) So it fits the prostitution theme.
Hm, didnt know that prostitution was the theme of the song but most prostitutes would call their clients by using tu and not vous.
*Voulez vous coucher avec moi ?*sounds more like casual sex offered to a total stranger, but not prostitution IMO.
Or a request for a three(or more)some?
This is in New Orleans, not France.
And, of course, this is probably where our word ‘couch’ came from…
He met Marmalade down on old Moulin Rouge
strutting her stuff on the street.
She said “Hello, Hey Joe!
Wanna give it a go?”
Gitchy-gitchy yaya dada (Get your yayas, daddy!)
Gitchy-gitchy yaya here (Get your yayas here)
Mocha choca latta yaya (latte-coffee-colored yayas (Marmalade’s Creole, as the next line says))
Creole Lady Marmalade.
She’s practically carnival-barkering her “assets”…this ain’t no casual pickup.
Slight technicalities (the best kind of technicalities):
Coucher means to place something down lengthwise.
Se coucher means to go to bed. Or to move your self from a vertical position to a horizontal one. You don’t technically have to sleep after having done so, but this is the common meaning. If you’re just relaxing in front of the television, you would use s’allonger.
Hi, Opal!
Coucher avec is a slang term, meaning to sleep with. Using vous in any context this word is appropriate is somewhat comical.
Dormir is to sleep, the actual biological phenomenon where you lose consciousness and so on.
S’endormir is to fall asleep. Also, metaphorically, to die.
They’re called “sleeping policemen” in Britain, too.
It’s like those French people have a word for everything!
Yeah, and it’s like they have a word that’s different from the word that we use. It’s like they speak a different language or something.
So if the right translation to English is “Any of ya’ll want a piece of this?”, then vous might be appropriate.
And, if the OP still has trouble, remember you’re asking Frère Jacques ‘Dormez-vous?’. Which means dormir is the one that means unconscious, as you wouldn’t need to ask someone if they’re lying down. (And of course, as Brother Jack is a monk, he’s clearly not going to coucher avec anyone.
Nitpick – “vous” doesn’t necessarily indicate a difference in status, but social distance versus familiarity. You call a person you don’t know “vous” not because you or they are socially superior, but because you don’t know one another well enough for that kind of familiar language.
(Interestingly, although Quebecers appear to use “tu” more readily than in France – I frequently get tutoied by store clerks and so forth – our advertisements seem to me to use “vous” more than they do in France.)
That’s true now, with all the social leveling of the 20th century… but in the old days, when society was more stratified? Vous was used by servants toward masters, wasn’t it?
Although it may not be quite to the point in this case, I think it might be worth pointing out to the OP that there is nothing at all odd about a language containing synonyms.