Etymology of Claus
Claus came from the Dutch Klaas, from Middle Dutch Niklaas, which derives from the Greek name Nikolas (or Nicholas) from Nikolaos. Nikolaos is a combination of two words, namely, Nike (victory) and Laos (people). So Nikolaos literally means victory of the people.
The real Saint Nicholas (Gr.: Ayios Nikolaos; Άγιος Νικόλαος) (15/Mar/270 - 6/Dec/346) is the common name for Nicholas of Myra, a saint and Bishop of Myra (in Asia Minor). Because of the many miracles attributed to his intercession, he is also known as Nicholas the Wonderworker. He had a reputation for secret gift-giving, such as putting coins in the shoes of those who left them out for him.
In modern Greek
a) Nikolaos (shrt.: Nikos): Nicholas, Nick [Νικόλαος]
b) Nike: victory, nike [Νίκη]
c) Laos: people [Λαός]
Nikolaos (Νικόλαος) --> Nikolas --> Niklaas --> Klaas --> Claus
More (with icon of the real Saint Nicholas) in: http://ewonago.blogspot.com/