What is "going down on"

Usage examples of "going down on".

The shoe went slowly round the table, each banker in turn going down on that dread third coup which, for some reason, is the sound barrier at chemin de fer which must be broken if you are to have a run.

Denoriel cried, covering the room in three bounds and going down on his knees on the little step stool Elizabeth used to climb into bed.

But all things considered, what good can it do the lady Aldonza Lorenzo, I mean the lady Dulcinea del Toboso, to have the vanquished your worship sends or will send coming to her and going down on their knees before her?