His head-chef, Hadji Hasan, was a very choosey and careful person in his profession and one day, one guest found a hair in his dish and this event turned his head-chef crazy.
This fact made the head-chef really very angry and his head-chef aligned all of the employees in a line and gave them a penalty.
Next day, all employees came to restaurant with baldheads. Mehmet learned his lesson from this event and he took his share also from this penalty and after Mehmet's hairs were cut-off, a V shaped scar appeared on his head, as this scar was remained him from a traffic accident, which he had in his childhood.
Shape of this scar meant "seven" in the old Turkish alphabet and this fact drew attention of his head-chef and he added the prefix 7 before his name and gave him the nickname of 7Mehmet and his lifelong, this 7 had never been deleted. So, the adventure of 7Mehmet started.