Where does “vasstett” come from?

vasstett (Norwegian Bokmål) comes from Norwegian Bokmål tett, from Old Norse þéttr, from Proto-Germanic þinhtaz, from Proto-Indo-European tenkt-, from Proto-Indo-European ten- — to stretch, to extend.

Ancestry of “vasstett”, step by step

Step	Language	Word	Meaning
1	Norwegian Bokmål	tett	tight; close; dense
2	Old Norse	þéttr	tight, watertight
3	Proto-Germanic	þinhtaz	tight
4	Proto-Indo-European	tenkt-	dense, thick, tight
5	Proto-Indo-European	ten-	to stretch, to extend

Every word from Proto-Indo-European ten- →Every word from Proto-Indo-European tenkt- →Every word from Proto-Germanic þinhtaz →