Meaning

originFrom Middle English lune, borrowed from Old Norse logn (“windstillness”), from Proto-Norse *lugna, meaning "place where the water is smooth", ultimately from Proto-Indo-European *lewk- (“bright”), referring to shining water. Germanic cognates include Icelandic lón, Danish lyn (“lightning”), Swedish lugn (“calm water”).

Etymology from Wiktionary, CC BY-SA 3.0