The town is located in Kenesh Na River (Kn? Ná), hence the name (Kně? Nou is a noun variant)
"nad" is a preposition, which means beside. ...
Rychnov is a common place name in the Czech Republic, so it needs to be represented by "on the banks of the Knezhna River".
It turns out that this place belongs to Austria-Germany Bohemia, so it has a German name Reichenau an der Knieschna. At present, Czech place names are basically copied from German and expressed in Slavic.