Until the 17th century it was called Svartmunka - or Svartbrödra - ("black monks/brothers"), and, because there are no records of the Dominican friars being referred to as "black men", the only reasonable explanation for the present name of the street is an attempt to create an analogy to Köpmangatan ("The Merchant's Street", or literally "buyer-man-street"), a street also leading from Stortorget.
Historically, this street was known as Svartmunka - or Svartbrödra - ("black monks/brothers") until the 17th century. The most plausible reason for its current name is a reference to Köpmangatan ("The Merchant's Street"), another street connected to Stortorget.