The word first entered English by the end of the fourteenth century, from Latin, and before Latin, Greek. Its earliest English use named something familiar to anyone who looked up on a clear night. The Greek source carried a specific meaning more striking than the modern sense suggests.
Latin borrowed the word directly from Greek, without passing through French. By the fifth century it already named a specific, everyday feature of the night sky before it reached English.
Behind the word lay a Greek adjective meaning milky, formed from the noun gala, meaning milk. That word traces to a Proto-Indo-European root, *g(a)lag-, with the same meaning. The full Greek phrase named the milky circle of starlight that medieval observers saw stretching across the heavens.
LACTOSE and LETTUCE share the same root, meaning 'milk'. LACTOSE entered English in the 1840s, coined in French from Latin, naming the sugar found in milk. LETTUCE entered English in the thirteenth century, from Old French and Latin, naming the salad leaf for the milky sap that runs from its stem.
