неде́льный (Russian) comes from Russian неде́ля, from Old East Slavic недѣлꙗ, from Proto-Slavic neděľa, from Proto-Slavic dělo, from Proto-Slavic děti, from Proto-Balto-Slavic dḗˀtei, from Proto-Indo-European dʰeh₁- — to do, put, place.
неде́льный (Russian): a week's, weekly