E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Covering the Face.
No malefactor was allowed, in ancient Persia, to look upon a king. So, in Esther vii. 5, when Haman fell into disgrace, being seen on the queens divan, they instantly cover Hamans face, that he might not look on the face of Ahasuerus.
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In India a low caste man covers his mouth when speaking to one of high caste.