The Collaborative International Dictionary
do-si-do \do`-si`-do"\, n. [from dos-[`a]-dos, back to back.] a movement in square-dancing in which two dancers move around each other in a back-to-back position, and return to their original places.
Douglas Harper's Etymology Dictionary
1929, from French dos-à-dos "back to back" (see dossier).
WordNet
n. a square-dance figure; two dancers approach each other and circle back to back before returning to their original places
Wikipedia
Do-si-do (, ), dosado, or dos-à-dos (see spelling below) is a basic dance step in such dances as square dance, contra dance, polka, various historical dances, and some reels.
The term is a corruption of the original French term dos-à-dos for the dance move, which means "back to back", as opposed to "vis-à-vis" which means "face to face".
It is probably the most well-known call in square dancing aside from, perhaps, " Promenade".
Usage examples of "do-si-do".
We're going to do-si-do, allemand left, and then tell the fiddler he's a rooster-dick motherfucker.