Harald's last name is actually Gormsson, but people called him 'Harald Bluetooth' instead of 'Harald Gormsson'. Harald's nickname was first recorded in 1140.
There are many reasons and theories why Harald has that nickname but the most common one is the fact that Harald had a bad tooth and it looked blue. Another reason is that Harald actually had a nickname called the 'dark chief' and because dark means blue his name was really 'Blue Chief'. The third reason Harald has the nickname is because he was a member of the royal family of Denmark and he wore a lot of blue, symbolizing royalty.
There are many reasons and theories why Harald has that nickname but the most common one is the fact that Harald had a bad tooth and it looked blue. Another reason is that Harald actually had a nickname called the 'dark chief' and because dark means blue his name was really 'Blue Chief'. The third reason Harald has the nickname is because he was a member of the royal family of Denmark and he wore a lot of blue, symbolizing royalty.
How Harald's initials in runes got to do with the Bluetooth company