RITUAL IMPURITY, specifically menstrual (Leviticus 15:19-24) — and by extension anything that must be kept at a distance. ⚠ Lamentations plays on it: verse 8 says Jerusalem became a nidah (from a root meaning to shake the head, so 'an object of head-shaking') and verse 17 says she became a niddah among the nations. The two words are near-identical and the poem almost certainly means both at once. The versions split badly here — KJV 'removed' at v8 and 'a menstruous woman' at v17; ASV 'an unclean thing'; NWT 'an object of disgust' — which is why this translation renders each verse as it stands and notes the play. → first discussed at Lamentations 1:8