środa isn't a good example, but wtorek, czwartek and piątek (second, fourth and fifth respectively) all point to Monday being the beginning of the week in Polish and no name points toward Sunday being the first day of the week.
I'm afraid you are wrong here. Środa
is a perfect example of the thesis that Sunday is the first day
of the week. Names of other days in Polish point to Sunday and not Monday,
with Poniedziałek ("po niedzieli") as the day first day after Sunday
; Wtorek as the second day after Sunday
(not the second day of the week); czwartek as the fourth day after Sunday; and piątek as the fifth day after Sunday. I'd say it is a bit magalomaniacal to ignore the whole tradition of mankind in which, as the other poster pointed out, the Sun was at the centre of our ancestors' world. Putting Monday first is the invention of the modern business world who counts Money
first and Nature
second, so it's understandable that for practical reasons it prefers Monday as the first place on the agenda of a busy week.
The Christian world also refers to Sunday as the first day of the week. God rested on the seventh day of the week and this was of course Saturday (sabbath) [although, I think, God did not mind how we would call it]. Christian people of the first centuries after Christ decided, in commemoration of the ressurrecion of Jesus which happened on Sunday, to move the celebration of the Day of Rest from the seventh day of the week (Saturday) to the first day of it (Sunday).