Where does “ngã tư” come from?

ngã tư (Vietnamese) comes from Vietnamese ngã, from Chinese 俄, from Manchu ᠣᡵᠣᠰ, from Classical Mongolian ᠣᠷᠤᠰ᠋, from Middle Mongolian 斡羅思, from Old East Slavic Русь, from Finnish ruotsi, from Proto-Finnic *roocci — to row; to separate; loose, sparse, rare.

ngã tư (Vietnamese): four-way intersection; crossroads

Definitions

four-way intersection; crossroads

Ancestry of “ngã tư”, step by step

ngã tư traces back through two separate lines of ancestry.

via Vietnamese ngã

Step	Language	Word	Meaning
1	Vietnamese	ngã	to fall; Short for thanh ngã; an intersection
2	Chinese	俄	—
3	Manchu	ᠣᡵᠣᠰ	Russian
4	Classical Mongolian	ᠣᠷᠤᠰ᠋	—
5	Middle Mongolian	斡羅思	—
6	Old East Slavic	Русь	Rus; Ruthenia
7	Finnish	ruotsi	Swedish
8	Proto-Finnic	*roocci	Swede originally anyone from Roslagen
9	Old Swedish	roþs-	related to rowing
10	Old Norse	róðr	rowing
11	Proto-Germanic	rōþrą	oar; rudder
12	Proto-Indo-European	h₁reh₁-	to row; to separate; loose, sparse, rare

via Vietnamese từ

Step	Language	Word	Meaning
1	Vietnamese	từ	from, since; at, in; word
2	Chinese	字	—
3	Chinese	母	—
4	Proto-Sino-Tibetan	*məʔ	mother

Every word from Proto-Indo-European h₁reh₁- →Every word from Old Swedish roþs- →Every word from Proto-Finnic *roocci →