An Etymological Dictionary of the German Language/Sack
Sack, m., ‘sack, bag, pocket,’ from the equiv. MidHG. sac (gen. sackes), OHG. sac (gen. sacches), m.; corresponding to the equiv. Goth. sakkus, m., OIc. sekkr, m., AS. sœcc, m., E. sack, and Du. zak. A loanword from Lat. saccus (Ital. sacco, Fr. and OIr. sac), which came through the medium of Gr. σάκκος, from the Hebr. and Phœnic. sak. The Lat. word seems to have been introduced into G., through commercial intercourse with Roman merchants, at a very early period (in Cæsar's time?), probably contemporaneously with Arche, Kiste, and Schrein.