The tale of how the Milky Way galaxy got its name depends on the mythology you read.
In Irish mythology, for example, the main name for the galaxy is Bealach na Bó Finne, or Way of the White Cow. The galaxy was regarded as a reflection of the River Boyne, an important waterway in Irish culture.
In Armenian mythology, the Milky Way is called the Straw Thief’s Way. The god Vahagn stole straw from King Barsham and brought it to Armenia during a cold winter, Armenians believed. The galaxy represents the straw Vahagn spilled on his way back to the country.