Thomas Aquinas Commentary Lamentations 2:16

"All thine enemies have opened their mouth wide against thee; They hiss and gnash the teeth; they say, We have swallowed her up; Certainly this is the day that we looked for; we have found, we have seen it." — Lamentations 2:16 (ASV)

Here he presents the insults of their enemies: your enemies have opened their mouth, by accusing; your enemies, Idumeans, Moabites, and others; they have hissed, by disparaging; and gnashed with the teeth, by threatening; we will swallow her up, by insulting. They have opened their mouths against me, as a lion ravening and roaring (Psalms 21:14). Nebuchadnezzar king of Babylon has eaten me up, he has devoured me (Jeremiah 51:34). They said, well done, well done, our eyes have seen it (Psalms 34:21).