Apparently it is named after the Moon, just as in English. Moon, in Spanish, is "luna".
"Es lunes" is Spanish for "It's Monday".
lunes
"Monday" in Spanish is "el lunes", and is not capitalized.
Lunes
Lunes
Lunes.
You can say "ayer fue lunes". Note that days of the week are not capitalized in Spanish.
Lunes lanzó viernes = Monday threw Friday de lunes a viernes = Monday through Friday
Lunes
Estare a casa el lunes = (I'll) be home Monday Be home Monday (imperative) = Este a casa el lunes
"Hoy es el lunes" means "Today is Monday" in Spanish.
lunes a sábado