Rashi: It is like She'oncha (your desolation).

Radak (Melachim II, 19:28) #1: This is like She'ancha (your roar). The Nun is doubled due to the exceeding noise. Also R. Yonah and Targum Yonasan hold like this.

Radak (Melachim II, 19:28) #2: The simple meaning is your serenity. His rage was because he was [initially] serene.

Rashi (Yeshayah 37:29): It is a ring put in the lip ¹ of an unruly animal, to lead it via it.

Rashi (Melachim II, 19:28): It is like a Shir (chain) via which one leads an unruly animal damage. 'All Ba'alei Shir (animals normally led via a chain) may go out with a Shir on Shabbos (Shabbos 51b).

Radak (Melachim II, 19:28): It is an iron hook used to trap fish. Its end is like a needle; it pierces the fish's nose and jaws, and via it one removes the fish from the water. This is like "uv'Cho'ach Tikov Lecheyo" (Iyov 40:26), "v'Nasati Chachim bi'Lchayecha" (Yechezkel 29:4).

Rashi, based on Targum Yonasan: It is an iron ring. It goes through [a hole pierced in the wall in the middle of] the nostrils ¹ , like it was taught, a camel goes out with a Chotem (Shabbos 51b).

Radak (Melachim II, 19:28, based on Targum Yonasan): It is an iron bit put in an animal's mouth to lead it. The Targum is Zemam, like the Targum of "v'Resen Mas'eh" (Yeshayah 30:28). Hashem told Sancheriv, I will show you that you are in My Reshus. I will lead you where I want, like one leads an animal and pulls it where he wants, and like a fisherman pulls a fish from the water, through a stratagem.

Malbim: They are (a) to stop him from going elsewhere until [he gets to] Yerushalayim, and (b) to stop him from blaspheming more, respectively.

Radak (Melachim II, 19:28): It is the path in which you will come. This message was sent to Sancheriv, who went to fight Melech Kush. After the war, he returned to Yerushalayim. He will return [to Ashur, after his camp is stricken].