Bluetooth, the wireless technology, was named after Scandinavian King Harald “Bluetooth” Gormsson, nicknamed because he had a rotten "blue-black" tooth.
The story goes that during a meeting betweeen industry leaders Intel, Ericsson and Nokia in 1996 to plan the standardization of the short-range radio technology, Jim Kardach from Intel suggested the codename Bluetooth. He was later quoted as saying, “King Harald Bluetooth was famous for uniting Scandinavia just as we intended to unite the PC and cellular industries with a short-range wireless link.”
The name was only supposed to be a placeholder until marketing came up with something bettter but it stuck. The logo is a binding of the runes (Hagall) (ᚼ) and (Bjarkan) (ᛒ), Harald’s initials.
Sources: Bluetooth website