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.
In India a low caste man covers his mouth when speaking to one of high caste.