Where does “Mercurii (dies)” come from?

Mercurii (dies) (Latin) comes from Latin dies Mercurii, from Latin dies, from Latin diem, from Proto-Italic djēm, from Proto-Italic *djous, from Proto-Indo-European dyḗws, from Proto-Indo-European dyéws, from Proto-Indo-European dyew- — to be bright; sky, heaven.

Ancestry of “Mercurii (dies)”, step by step

StepLanguageWordMeaning
1Latindies MercuriiWednesday
2LatindiesA day, "particularly:"
3Latindiemaccusative singular of diēs
4Proto-Italicdjēmaccusative singular of *djous
5Proto-Italic*djous
6Proto-Indo-Europeandyḗwssky, heaven; sky god
7Proto-Indo-Europeandyéwssky, heaven
8Proto-Indo-Europeandyew-to be bright; sky, heaven
Every word from Proto-Indo-European dyew-Every word from Proto-Indo-European dyéwsEvery word from Proto-Indo-European dyḗws