[thaumasiotes]

Well, wiktionary does call them cognates, if you follow the links around.

Old English swige < proto-West-Germanic swiga ; German schweigen < proto-West-Germanic swigen < swiga

(Following the links around on wiktionary may, in general, lead to self-contradictory results.)

[niwis]

In Limburgs, still today: Zwieg!: Shut up, zwiegen: Not saying anything.