Origin of the word/root 'del'

Question

As I was contemplating the Norwegian word "del," which means "part" or "portion," it occurred to me that there is the same root in Russian, and that it means the same thing. I looked up "del" and "делить" (the verb formed from the root "дел"), and here's what I got:

1. del - Norwegian:

From Middle Low German dēl, deil, from Old Saxon dēl, from Proto-Germanic *dailą, *dailiz (“part, portion, deal”).

2. делить - Russian

From Proto-Slavic *děliti (“to divide”), from Proto-Balto-Slavic *doyl-, from Proto-Indo-European *dʰayl-, *dʰoyl-. Cognates include Old English dǣlan (English deal) and Lithuanian dailyti.

How do these chains get constructed, and why don't these two lead to the same common ancestor?

Answer 1

These words are related, but they do not have any known cognates outside of Germanic and Balto-Slavic. “Proto-Indo-European *dʰayl-, *dʰoyl-“ (as posited on Wikipedia) is highly uncertain. It has been suggested that it is a substrate word.

See the etymology section here: https://www.dwds.de/wb/Teil

Answer 2

They definitely do go to the same common ancestor, just the first etymology you found does not go deep enough.

Norwegian del is reconstructed to proto-germanic dailiz, but that originates from PIE *dhail-, the etymon for the Slavic děliti.

DEL in Norwegian

DAILIZ in Proto-Germanic

DĚLIŤ in Russian