This is the 2655th most frequent Dutch word.
köln
The Dutch word "Köln" refers to the German city of Cologne.
Here, 'Keulen' refers to the city of Cologne in Germany, used as a proper noun indicating a place.
Ik ging vorige maand naar Keulen.
I went to Cologne last month.
In this sentence, 'Keulse' is an adjective form derived from 'Keulen', describing something related to Cologne.
De Keulse Dom is een prachtig voorbeeld van gotische architectuur.
The Cologne Cathedral is a stunning example of Gothic architecture.
Here, 'Keulen' once again refers to the city of Cologne as a proper noun and specifies the origin of the souvenir.