Wikipedia
The Greek name for the Milky way (Γαλαξίας Galaxias) is derived from the word for milk (γάλα, gala). One legend explains how the Milky Way was created by Heracles when he was a baby.[2] His father, Zeus, was fond of his son, who was born of the mortal woman Alcmene. He decided to let the infant Heracles suckle on his divine wife Hera's milk when she was asleep, an act which would endow the baby with godlike qualities. When Hera woke up and realized that she was breastfeeding an unknown infant, she pushed him away and the spurting milk became the Milky Way.
A story told by the Roman Hyginus in the Poeticon astronomicon (ultimately based on Greek myth) says that the milk came from the goddess Ops (Greek Rhea), the wife of Saturn (Greek Cronus). Saturn swallowed his children to ensure his position as head of the Pantheon and sky god, and so Ops conceived a plan to save her newborn son Jupiter (Greek Zeus): She wrapped a stone in infant's clothes and gave it to Saturn to swallow. Saturn asked her to nurse the child once more before he swallowed it, and the milk that spurted when she pressed her nipple against the rock eventually became the Milky Way.[5]