There is a kind of chocolate bar called a Galaxy. There is also a kind of chocolate bar called a Milky Way. I'm not sure on what basis these names were chosen. Tabloid newspapers also pilfer the nomenclature of astronomy. I suppose the Milky Way suggests milk chocolate.
Pretty much every European language refers to the Milky Way as the Milky Way. In France it is la voie lactée, in German the Milchstraße, and in Welsh it is the Llwybr Laethog, because the Welsh language was invented by somebody playing a bad hand at Scrabble.
The milk comes from the myth that the pale strip of night sky was created when Hera was breast-feeding Hercules and overlactated.
In ancient Greek it was also called milk. The Greek for milk was gala, but the genitive of gala was galaktos. This means two things: first galactic is the etymological brother of lactating; and, second, the only difference between the two chocolate bars is that one of them is Greek.
That's how it happened