Why is the Software Called MariaDB?

The 'MySQL' name is trademarked by Oracle, and they have chosen to keep that trademark to themselves. The name MySQL (just like the MyISAM storage engine) comes from Monty's first daughter My. The first part of 'MySQL' is pronounced like the English adjective, even if this doesn't match the correct pronunciation of the Finnish name.

MariaDB continues this tradition by being named after his younger daughter, Maria.

The name Maria was initially given to a storage engine. After MariaDB was started, to avoid confusion, it was renamed to Aria. The new name was decided as a result of a contest.