Serena Williams’ trademark grunt came from her hero-worship of Monica Seles’ “cool” court groans. The tennis icon, 42, became renowned for her ear-shattering match cries throughout her career, and has now said it was inspired by watching fellow tennis great Monica, 50, who won eight of her nine major titles while a teen representing her native Yugoslavia. Serena – who is now retired from tennis and is raising her daughters Olympia, six, and 11-month-old Adira, who she has with her 41-year-old husband Alexis Ohanian – said on the ‘Hot Ones’ YouTube show hosted by Sean Evans: “So I grunt because…