Where does “mānundag” come from?

mānundag (Old Saxon) comes from Proto-Germanic *mānini dag, from Latin dies Lūnae, from Ancient Greek σελήνη, from Ancient Greek Σέλας.

Ancestry of “mānundag”, step by step

Step	Language	Word	Meaning
1	Proto-Germanic	*mānini dag	—
2	Latin	dies Lūnae	—
3	Ancient Greek	σελήνη	moon; month; a moon-shaped cake
4	Ancient Greek	Σέλας	—

mānundag — Etymology, Origin & Word History | Etymology Explorer