Etymology of Monday

we all know that monday is usually the start of the work week, and we all know that monday feels like it comes too early. but how many of you know how monday got to be called monday? centuries ago our ancestors used to call it one of these names:
a) mud day
b) moon day
c) man day
d) mood day
if you know the right answer you get double punches today! the answer to wednesday's trivia: wayne fontana and the mindbenders, queen, the alan parsons project