"grub". And the password is in /etc/grub.d/01_PASSWORD.
According to GRUB's documentation, "requiring authentication at the boot loader level would only serve to make it difficult to recover broken systems" in most environments: https://www.gnu.org/software/grub/manual/grub.html#Security
To disable GRUB's password, comment or remove /etc/grub.d/01_PASSWORD and execute 'sudo update-grub'.
