meolc

Old English meolc (also spelled milc and mioluc) descends from Proto-Germanic *meluks, from PIE *h₂melǵ-, meaning to wipe, to stroke, to press out. The root described the physical action: the milker's hand pulling down along the udder. The liquid was named after what you did to get it, not what it was. This is surprisingly common in old food words — butter likely comes from a root meaning "cow cheese," and cheese comes from a root meaning "to ferment." The process names the product.

Milk was central to the Neolithic revolution. When humans domesticated cattle, sheep, and goats between 8000 and 6000 BCE, they gained a renewable protein source that did not require slaughtering the animal. But early humans were lactose intolerant after childhood — the enzyme lactase shut off after weaning. A genetic mutation that kept lactase active into adulthood appeared around 5000 BCE in populations near the Balkans and spread rapidly through Europe. Milk tolerance was such a survival advantage that it reshaped the human genome in five thousand years.

The word traveled with the thing. Proto-Germanic *meluks became Old English meolc, Old High German miluh, Old Norse mjólk, and Dutch melk. Latin had its own unrelated word, lac (from PIE *glakt-), which gave French lait, Spanish leche, and Italian latte. So the Germanic and Romance milk words have completely different origins — a rare case where two major European language families reached for different metaphors to name the same substance.

English milk has accumulated centuries of metaphor. The land of milk and honey. The milk of human kindness (Shakespeare, Macbeth). Don't cry over spilt milk. Milk-toast (timid). To milk something (to extract value). The Milky Way — galaxias in Greek, from gala, milk — is a streak of spilled milk across the sky. Even the galaxy is named for what comes out of an udder.