The loading order of Bash startup files is first dependent on the type of shell that Bash think it is in.
A login shell is when the user logs in from tty (not through a GUI) or logs in remotely (e.g. through ssh).
A non-login shell is started in other ways such as gnome-terminal which is started by Gnome (it is a login shell that launched Gnome).
Note: The exception is OSX's Terminal.app which is treated as a login shell.
For non-login shells (e.g. gnome-terminal) the order is:
/etc/bash.bashrc
~/.bashrc
For login-shells (including Terminal.app) the order is:
/etc/profile and then first of: /etc/profile
Followed by the first of the following:
~/.bash_profile
~/.bash_login
~/.profile
