Where does “doi” come from?

doi (North Frisian) comes from Old Frisian dei, from Proto-West Germanic dag, from Proto-Germanic dagaz, from Proto-Indo-European dʰegʷʰ- — to burn; warm, hot.

doi (North Frisian): day

Definitions

Ancestry of “doi”, step by step

Step	Language	Word	Meaning
1	Old Frisian	dei	day
2	Proto-West Germanic	dag	day
3	Proto-Germanic	dagaz	day; name of the D-rune
4	Proto-Indo-European	dʰegʷʰ-	to burn; warm, hot

Every word from Proto-Indo-European dʰegʷʰ- →Every word from Proto-Germanic dagaz →Every word from Proto-West Germanic dag →