Why does it say "Chetz Shachut Leshonam"?
Rashi #1: It is drawn 1 like "Zahav Shachut" (refer to Melachim I, 10:16:3:1-2) and "v'Shachatah Setim" (Hoshe'a 5:2).
Rashi #2, Targum Yonasan 2 , Menachem: It is an expression of Shechitah (cutting off).
Radak: It is written Shochet, for they kill people via their Leshon ha'Ra - they gossip about others. It is pronounced Shachut, i.e. it is drawn on the sharpening stone to make it sharp. Chetz Shachut is deception.
Radak citing his father: Shachut is an adjective. Similarly, "Adam Ashuk b'Dam Nefesh" (Mishlei 28:17) is like Oshek.
Malbim: This is a tongue that speaks constantly like it wants and chooses. It can speak or refrain. It is compared to a bow that shoots arrows (words). They already accustomed themselves to speak deception constantly, so the tongue is no longer under their control. Rather, it is like an arrow in the archer's hand. The archer is the speaker. He moves his tongue like an archer shoots arrows. The arrow is Shachut (shot); it is too late to retract it.
Radak: This is because Shechitah must be in a drawing motion - like it says, if one sliced off the head at once, the Shechitah is Pasul, for it says "Chetz Shachut Leshonam", and Tana d'Vei R. Yishmael says that Shachut is drawn, like "Zahav Shachut" (Melachim I, 10:16).
Radak: Targum Yonasan is Macharif. This is like Sachina Charifa (Bava Basra 111b) - it is sharp and cuts a tiny piece.
Why does it say "Mirmah Diber"?
Malbim: The guile is personified, and speech is attributed to it. It is the speaker. It already spoke, pressed and drew the arrow (tongue), and he cannot hold back the tongue any more. I.e. deceptive speech became second nature, to the point that they cannot train themselves to speak Emes.
What is "uv'Kirbo"?
Rashi citing Targum Yonasan: In his innards.
Malbim: Amidst the talk, he sits in ambush to harm his friend.
