Monday \Mon"day\ (m[u^]n"d[asl]; 48), n. [OE. moneday, monenday, AS. m[=o]nand[ae]g, i.e., day of the moon, day sacred to the moon; akin to D. maandag, G. montag, OHG. m[=a]natag, Icel. m[=a]nadagr, Dan. mandag, Sw. m[*a]ndag. See Moon, and Day.]

The second day of the week; the day following Sunday.

Source: Webster's Revised Unabridged Dictionary (1913)