Bokeh is a word that describes blurry, quite large, often round blobs in the image, often as background of some focussed image part.
As an example see the Bokeh of these lights of a Christmas tree.
“Bokeh” actually is the image of typically point sized Objects in a distance far outside the DOF, most often point size objects at infinity while the lens is focussed on some near distance or point sized object in the foreground when the lens is focussed on infinity.
A diagram explains this best :
The lowest large dot on the right is an example for Bokeh.
The shape of the Bokeh is the shape of the physical Iris. This is why many customers prefer round iris shapes
The Bokeh has ring shape here, because the image was taken with by a mirror lens, so that the iris center wasn’t exposed to light.