Where does “Fettdonnerstag” come from?

Fettdonnerstag (German) comes from German Donnerstag, from Middle High German donerstac, from Old High German donarestag, from Proto-Germanic *Þunras dag, from Latin dies iovis, from Latin diēs, from Proto-Italic djēm, from Proto-Italic *djous — to be bright; sky, heaven.

Fettdonnerstag (German): Fat Thursday

Definitions

  1. Fat Thursday

Ancestry of “Fettdonnerstag”, step by step

Fettdonnerstag traces back through two separate lines of ancestry.

via German Donnerstag

StepLanguageWordMeaning
1GermanDonnerstagThursday
2Middle High GermandonerstacThursday
3Old High GermandonarestagThursday
4Proto-Germanic*Þunras dag—
5Latindies iovisThursday
6LatindiēsA day, particularly
7Proto-Italicdjēmaccusative singular of *djous
8Proto-Italic*djous—
9Proto-Indo-Europeandyḗwssky, heaven; sky god
10Proto-Indo-Europeandyéwssky, heaven
11Proto-Indo-Europeandyew-to be bright; sky, heaven

via German fett

StepLanguageWordMeaning
1Germanfettfat; rich, containing a lot of fat; bold
2Middle Low Germanvet—
3Old Saxonfētid—
4Proto-West Germanicfaitidfattened, made fat
5Proto-West Germanicfaitfat
6Proto-Germanicfaitazfat
7Proto-Indo-EuropeanpoyH-—
8Proto-Indo-EuropeanpeyH-fat, milk
Every word from Proto-Indo-European dyew- →Every word from Proto-Indo-European dyéws →Every word from Proto-Indo-European dyḗws →