Where does “долг” come from?

долг (Macedonian) comes from Proto-Slavic dь̀lgъ, from Proto-Balto-Slavic dílˀgas, from Proto-Indo-European dl̥h₁gʰós — long.

долг (Macedonian): long, lengthy; debt

Definitions

Step	Language	Word	Meaning
1	Proto-Slavic	dь̀lgъ	—
2	Proto-Balto-Slavic	dílˀgas	long
3	Proto-Indo-European	dl̥h₁gʰós	long

долг — Etymology, Origin & Word History | Etymology Explorer