This is along the same general idea as the Persian/Farsi day names, you've got Jummah which is the western Friday (Islamic day of rest), then the rest of the days are named shanbe, yakshanbe, doshanbe, sehshanbe, and so on.

shanbe = day (first day of the week after Jummah)

yak = one

do = two

seh = three

Literally just day one, day two, day three.

You count upwards in day number until you reach six, then it's Jummah again and it resets.

The city of Dushanbe, Tajikistan being part of the historical extent of the Persian empire and language is literally just named second day.

The same roughly applies to Arabic: Sunday (derived from one) to Thursday (derived from five).

The word for Friday seems to be derived from “gathering” (probably due to weekly Islamic mass) and Saturday seems to derived from “sleep” (?).