MACK was a Swedish company who manufactured pumps for gas stations. The name was an acronym for the names of the founders Mathiasson, Andersson, Collin and Key.
By 1914 their pumps had become the leading brand in Sweden, and this eventually led to "mack" becoming a generic name for all gas pumps and eventually gas stations as a whole.
Today the company is gone but "mack" is still in common usage. A popular example of this was the TV-series Macken.
References
MACK (Swedish company) Wikipedia(Text) CC BY-SA