Milky means pale and cloudy like milk. Milky tea, a milky liquid, milky white.
Of a drink it means containing a lot of milk, and how milky somebody takes their tea is a small but genuine subject of British negotiation. Of a liquid or a stone it means cloudy rather than clear: milky water, milky quartz. The Milky Way is our galaxy, named for the band of faint light across the sky, which is the galaxy seen edge on from inside it. Note milkiness.
1adjectivemilkyPale and cloudy like milk.
“The water in the glacier lake was a strange milky blue.”
2adjectivecontainingContaining a lot of milk.
“I like my coffee milky, with just one sugar.”
milky is a quality of cloudy paleness.
Old English meolcig is milk plus -y. The Milky Way translates Latin via lactea, which itself translates the Greek — three languages independently deciding the sky looked like spilt milk.
Proto-Germanic
*melukigaz
Proto-West Germanic
*melukig
Old English
*meolciġ
Middle English
mylky
English, today
milky
From Middle English mylky, melky; from Old English meolciġ, from Proto-West Germanic melukig, from Proto-Germanic melukigaz. Equivalent to milk + y. Cognate with stq moalkig (“milky”), West Frisian molkich (“milky”), Dutch melkig (“milky”), German Low German melkig (“milky”), German milchig (“milky”), Danish mælkig (“milky”), Swedish mjölkig (“milky”), Icelandic mjólkugur (“milky”). a doublet of milchig.
Etymology from Wiktionary, CC BY-SA