Thayer's
STRONGS NT 4526: σάκκοςσάκκος (Attic
σάκος),
σάκκου,
ὁ, Hebrew
שַׂק (cf. Fremdwörter, under the word),
a sack (Latin
saccus) i. e.
a. a receptacle made for holding or carrying various things, as money, food, etc. (; Leviticus 11:32).
b. a coarse cloth (Latincilicium), a dark coarse stuff made especially of the hair of animals (A. V. sackcloth): Revelation 6:12; a garment of the like material, and clinging to the person like a sack, which was usually worn (or drawn on over the tunic instead of the cloak or mantle) by mourners, penitents, suppliants, Matthew 11:21; Luke 10:13, and also by those who, like the Hebrew prophets, led an austere life, Revelation 11:3 (cf. what is said of the dress of John the Baptist, Matthew 3:4; of Elijah, 2 Kings 1:8). More fully in Winers RWB under the word Sack; Roskoff in Schenkel 5:134; (under the word in B. D.; also in McClintock and Strong. (From Herodotus down.))