The old galaxy.
No human referred to the Milky Way Galaxy like this in the past. Humanity never actually used this stuffy name of its home galaxy that often either because there was no need to make the distinction.
In the past, ancient humans only referred to the only sun as 'the sun' and the only moon as 'the moon' before they traversed the stars. They were forced to use more unique designations in order to distinguish between stars and moons.
In the same way, humans took a long time to refer to the Milky Way Galaxy as 'the galaxy' before they expanded their reach yet again.
The opening of the Red Ocean and the spread of humanity to an entirely different galaxy, if only a miniature-sized one, caused many humans to develop the need for greater differentiation!
Since calling the Milky Way Galaxy by this clunky name all of the time became tiresome, humans had taken to referring to it as the old galaxy for convenience.
