среда means the middle of the week in Russian, like Mittwoch in German. It does not mean anything in Hungarian, except the name of the 3rd day. You may recognize the old Persian word 'bazaar' in the name of the 7th day: 'vasárnap' in Hungarian, i.e. 'market day'. This came via Turkish, in which Sunday is still called 'Pazar'.
I don't think that the word "szerda" is Turkic origin. It's pure Slavism. "Çarşamba" is originally a Persian word, as well as the other days of the week in the most of the Turkic languages. Magyar nyelv has a lot of Turkic words, i think mostly from Bulgaric branch. But there are also words that must understand every Turk. For example (Magyar-Kazakh-English): Alma-alma-apple, anya-ana-mother, balta-balta-ax, béka-baqa-frog, homok-qum-sand, tenger(bulgaric)-teñiz-sea, kék-kök-blue, sárga-sarı-yellow, ökör & bika -ögiz & buqa-ox & bull, teve-tüye-camel, szel-jel-wind, szakáll-saqal-beard, macska - mısıq - cat etc. :)