Sack is a pure Hebrew word, and has spread into many modern languages. Sackcloth is a very coarse stuff, often of hair, Re 6:12. In great calamities, in penitence, in trouble, the Jews, etc., wore sackcloth about their bodies, Ge 37:34; 2Sa 3:31; 1Ki 20:32; Mt 11:21. The prophets were often clothed in sackcloth, and generally in coarse clothing, Mt 11:21. The Lord bid Isaiah put off the sackcloth from about his body, and go naked, Isa 20:2. Zechariah says, Zec 13:4, that false prophets should no longer prophesy in sackcloth, (English translation, a rough garment,) to deceive the simple.

In time of joy, or on hearing good news, those who were clad in sackcloth cast it from them, and resumed their usual clothing, Ps 30:11.