Where does “maantaki” come from?

maantaki (Ingrian) comes from Finnish maanantai, from Old Swedish mānadagher, from Old Norse mánadagr, from Proto-Germanic *mānini dag, from Latin dies Lūnae, from Ancient Greek σελήνη, from Ancient Greek Σέλας — light, brightness, the bright flame or blaze of fire.

Ancestry of “maantaki”, step by step

Step	Language	Word	Meaning
1	Finnish	maanantai	Monday
2	Old Swedish	mānadagher	Monday
3	Old Norse	mánadagr	Monday
4	Proto-Germanic	*mānini dag	—
5	Latin	dies Lūnae	Monday
6	Ancient Greek	σελήνη	moon; month; a moon-shaped cake
7	Ancient Greek	Σέλας	light, brightness, the bright flame or blaze of fire

Every word from Ancient Greek Σέλας →Every word from Ancient Greek σελήνη →Every word from Latin dies Lūnae →