Wani or Wain word comes from Sanskrit language, root word Wania meaning Businessman or Shopkeeper. The term is used for traders and merchants. Wani mainly is a caste and a surname used in kashmir. The Wani's have different names given according to their field of trade. Wain or Wani is one of the most common and famous Surname of Jammu and Kashmir.It is not necessary that wani are muslims.They can be hindu there are many businessman in maharashtra who use surname wani.
References
Wani (surname) Wikipedia(Text) CC BY-SA