"Giessen" is nothing more than "to pour".
"Kippen" is "to tilt", or indeed "tip".
Different thingies. You may have to 'kipp' something to 'giess' its content over something. You can 'kipp' something without it resulting in 'giessen'.
As in: you may have to 'tip' a container to 'pour' its content over something. But when you tip your hat, it will only pour something when its pouring with rain.
The German thing is a pouring-machine, i.e. named after the action. While the English counterpart is named after the result.
(A "Geiss", by the way, is a "goat". A bit archaic word, but that's what it means.
So you were only one letter away from being absolutely right when you wrote "Geiss is also the word for coat" )